The double-bar graph shows the number of home runs hit by McGwire and Sosa during each month of the 1998 baseball season. At the end of which month were McGwire and Sosa tied in total number of home runs?

[asy]
draw((0,0)--(28,0)--(28,21)--(0,21)--(0,0)--cycle,linewidth(1));

for(int i = 1; i < 21; ++i)
{

draw((0,i)--(28,i));
}

for(int i = 0; i < 8; ++i)
{

draw((-1,3i)--(0,3i));
}

label("0",(-1,0),W);
label("3",(-1,3),W);
label("6",(-1,6),W);
label("9",(-1,9),W);
label("12",(-1,12),W);
label("15",(-1,15),W);
label("18",(-1,18),W);
label("21",(-1,21),W);

for(int i = 0; i < 8; ++i)
{

draw((4i,0)--(4i,-1));
}

filldraw((1,0)--(2,0)--(2,1)--(1,1)--(1,0)--cycle,gray,linewidth(1));
filldraw((5,0)--(6,0)--(6,10)--(5,10)--(5,0)--cycle,gray,linewidth(1));
filldraw((9,0)--(10,0)--(10,16)--(9,16)--(9,0)--cycle,gray,linewidth(1));
filldraw((13,0)--(14,0)--(14,10)--(13,10)--(13,0)--cycle,gray,linewidth(1));
filldraw((17,0)--(18,0)--(18,8)--(17,8)--(17,0)--cycle,gray,linewidth(1));
filldraw((21,0)--(22,0)--(22,10)--(21,10)--(21,0)--cycle,gray,linewidth(1));
filldraw((25,0)--(26,0)--(26,15)--(25,15)--(25,0)--cycle,gray,linewidth(1));

filldraw((6,0)--(7,0)--(7,6)--(6,6)--(6,0)--cycle,black,linewidth(1));
filldraw((10,0)--(11,0)--(11,7)--(10,7)--(10,0)--cycle,black,linewidth(1));
filldraw((14,0)--(15,0)--(15,20)--(14,20)--(14,0)--cycle,black,linewidth(1));
filldraw((18,0)--(19,0)--(19,9)--(18,9)--(18,0)--cycle,black,linewidth(1));
filldraw((22,0)--(23,0)--(23,13)--(22,13)--(22,0)--cycle,black,linewidth(1));
filldraw((26,0)--(27,0)--(27,11)--(26,11)--(26,0)--cycle,black,linewidth(1));

label("Mar",(2,0),S);
label("Apr",(6,0),S);
label("May",(10,0),S);
label("Jun",(14,0),S);
label("Jul",(18,0),S);
label("Aug",(22,0),S);
label("Sep",(26,0),S);
[/asy] [asy]
draw((30,6)--(40,6)--(40,15)--(30,15)--(30,6)--cycle,linewidth(1));
filldraw((31,7)--(34,7)--(34,10)--(31,10)--(31,7)--cycle,black,linewidth(1));
filldraw((31,11)--(34,11)--(34,14)--(31,14)--(31,11)--cycle,gray,linewidth(1));

label("McGwire",(36,12.5));
label("Sosa",(36,8.5));
[/asy]
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The double-bar graph shows the number of home runs hit by McGwire and Sosa during each month of the 1998 baseball season. At the end of which month were McGwire and Sosa tied in total number of home runs?

[asy]
draw((0,0)--(28,0)--(28,21)--(0,21)--(0,0)--cycle,linewidth(1));

for(int i = 1; i < 21; ++i)
{

draw((0,i)--(28,i));
}

for(int i = 0; i < 8; ++i)
{

draw((-1,3i)--(0,3i));
}

label("0",(-1,0),W);
label("3",(-1,3),W);
label("6",(-1,6),W);
label("9",(-1,9),W);
label("12",(-1,12),W);
label("15",(-1,15),W);
label("18",(-1,18),W);
label("21",(-1,21),W);

for(int i = 0; i < 8; ++i)
{

draw((4i,0)--(4i,-1));
}

filldraw((1,0)--(2,0)--(2,1)--(1,1)--(1,0)--cycle,gray,linewidth(1));
filldraw((5,0)--(6,0)--(6,10)--(5,10)--(5,0)--cycle,gray,linewidth(1));
filldraw((9,0)--(10,0)--(10,16)--(9,16)--(9,0)--cycle,gray,linewidth(1));
filldraw((13,0)--(14,0)--(14,10)--(13,10)--(13,0)--cycle,gray,linewidth(1));
filldraw((17,0)--(18,0)--(18,8)--(17,8)--(17,0)--cycle,gray,linewidth(1));
filldraw((21,0)--(22,0)--(22,10)--(21,10)--(21,0)--cycle,gray,linewidth(1));
filldraw((25,0)--(26,0)--(26,15)--(25,15)--(25,0)--cycle,gray,linewidth(1));

filldraw((6,0)--(7,0)--(7,6)--(6,6)--(6,0)--cycle,black,linewidth(1));
filldraw((10,0)--(11,0)--(11,7)--(10,7)--(10,0)--cycle,black,linewidth(1));
filldraw((14,0)--(15,0)--(15,20)--(14,20)--(14,0)--cycle,black,linewidth(1));
filldraw((18,0)--(19,0)--(19,9)--(18,9)--(18,0)--cycle,black,linewidth(1));
filldraw((22,0)--(23,0)--(23,13)--(22,13)--(22,0)--cycle,black,linewidth(1));
filldraw((26,0)--(27,0)--(27,11)--(26,11)--(26,0)--cycle,black,linewidth(1));

label("Mar",(2,0),S);
label("Apr",(6,0),S);
label("May",(10,0),S);
label("Jun",(14,0),S);
label("Jul",(18,0),S);
label("Aug",(22,0),S);
label("Sep",(26,0),S);
[/asy] [asy]
draw((30,6)--(40,6)--(40,15)--(30,15)--(30,6)--cycle,linewidth(1));
filldraw((31,7)--(34,7)--(34,10)--(31,10)--(31,7)--cycle,black,linewidth(1));
filldraw((31,11)--(34,11)--(34,14)--(31,14)--(31,11)--cycle,gray,linewidth(1));

label("McGwire",(36,12.5));
label("Sosa",(36,8.5));
[/asy]
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\text{August}
The double-bar graph shows the number of home runs hit by McGwire and Sosa during each month of the 1998 baseball season. At the end of which month were McGwire and Sosa tied in total number of home runs?

[asy]
draw((0,0)--(28,0)--(28,21)--(0,21)--(0,0)--cycle,linewidth(1));

for(int i = 1; i < 21; ++i)
{

draw((0,i)--(28,i));
}

for(int i = 0; i < 8; ++i)
{

draw((-1,3i)--(0,3i));
}

label("0",(-1,0),W);
label("3",(-1,3),W);
label("6",(-1,6),W);
label("9",(-1,9),W);
label("12",(-1,12),W);
label("15",(-1,15),W);
label("18",(-1,18),W);
label("21",(-1,21),W);

for(int i = 0; i < 8; ++i)
{

draw((4i,0)--(4i,-1));
}

filldraw((1,0)--(2,0)--(2,1)--(1,1)--(1,0)--cycle,gray,linewidth(1));
filldraw((5,0)--(6,0)--(6,10)--(5,10)--(5,0)--cycle,gray,linewidth(1));
filldraw((9,0)--(10,0)--(10,16)--(9,16)--(9,0)--cycle,gray,linewidth(1));
filldraw((13,0)--(14,0)--(14,10)--(13,10)--(13,0)--cycle,gray,linewidth(1));
filldraw((17,0)--(18,0)--(18,8)--(17,8)--(17,0)--cycle,gray,linewidth(1));
filldraw((21,0)--(22,0)--(22,10)--(21,10)--(21,0)--cycle,gray,linewidth(1));
filldraw((25,0)--(26,0)--(26,15)--(25,15)--(25,0)--cycle,gray,linewidth(1));

filldraw((6,0)--(7,0)--(7,6)--(6,6)--(6,0)--cycle,black,linewidth(1));
filldraw((10,0)--(11,0)--(11,7)--(10,7)--(10,0)--cycle,black,linewidth(1));
filldraw((14,0)--(15,0)--(15,20)--(14,20)--(14,0)--cycle,black,linewidth(1));
filldraw((18,0)--(19,0)--(19,9)--(18,9)--(18,0)--cycle,black,linewidth(1));
filldraw((22,0)--(23,0)--(23,13)--(22,13)--(22,0)--cycle,black,linewidth(1));
filldraw((26,0)--(27,0)--(27,11)--(26,11)--(26,0)--cycle,black,linewidth(1));

label("Mar",(2,0),S);
label("Apr",(6,0),S);
label("May",(10,0),S);
label("Jun",(14,0),S);
label("Jul",(18,0),S);
label("Aug",(22,0),S);
label("Sep",(26,0),S);
[/asy] [asy]
draw((30,6)--(40,6)--(40,15)--(30,15)--(30,6)--cycle,linewidth(1));
filldraw((31,7)--(34,7)--(34,10)--(31,10)--(31,7)--cycle,black,linewidth(1));
filldraw((31,11)--(34,11)--(34,14)--(31,14)--(31,11)--cycle,gray,linewidth(1));

label("McGwire",(36,12.5));
label("Sosa",(36,8.5));
[/asy]
train