The lateral surface area of the frustum of a solid right cone is the product of one-half the slant height ($L$) and the sum of the circumferences of the two circular faces. What is the number of square centimeters in the total surface area of the frustum shown here? Express your answer in terms of $\pi$.

[asy]
draw( scale(1,.2)*arc(origin,10,180,360) ) ;
draw( scale(1,.2)*arc(origin,10,15,165) , dashed ) ; //yes, there is a gap
draw( (-10,0)--(10,0) , dotted ) ;
label("20cm",(0,0),S);
draw((0,0)--(0,8));
label("8cm",(0,4),E);
draw( shift(0,8)*scale(1,.2)*circle(origin,4) ) ;
draw( (-4,8)--(4,8) , dotted ) ;
label("8cm",(0,8),N);
draw((-10,0)--(-4,8));
draw((10,0)--(4,8));
label("$L$",(5,4),NE);
[/asy]
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The lateral surface area of the frustum of a solid right cone is the product of one-half the slant height ($L$) and the sum of the circumferences of the two circular faces. What is the number of square centimeters in the total surface area of the frustum shown here? Express your answer in terms of $\pi$.

[asy]
draw( scale(1,.2)*arc(origin,10,180,360) ) ;
draw( scale(1,.2)*arc(origin,10,15,165) , dashed ) ; //yes, there is a gap
draw( (-10,0)--(10,0) , dotted ) ;
label("20cm",(0,0),S);
draw((0,0)--(0,8));
label("8cm",(0,4),E);
draw( shift(0,8)*scale(1,.2)*circle(origin,4) ) ;
draw( (-4,8)--(4,8) , dotted ) ;
label("8cm",(0,8),N);
draw((-10,0)--(-4,8));
draw((10,0)--(4,8));
label("$L$",(5,4),NE);
[/asy]
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
256 \pi
The lateral surface area of the frustum of a solid right cone is the product of one-half the slant height ($L$) and the sum of the circumferences of the two circular faces. What is the number of square centimeters in the total surface area of the frustum shown here? Express your answer in terms of $\pi$.

[asy]
draw( scale(1,.2)*arc(origin,10,180,360) ) ;
draw( scale(1,.2)*arc(origin,10,15,165) , dashed ) ; //yes, there is a gap
draw( (-10,0)--(10,0) , dotted ) ;
label("20cm",(0,0),S);
draw((0,0)--(0,8));
label("8cm",(0,4),E);
draw( shift(0,8)*scale(1,.2)*circle(origin,4) ) ;
draw( (-4,8)--(4,8) , dotted ) ;
label("8cm",(0,8),N);
draw((-10,0)--(-4,8));
draw((10,0)--(4,8));
label("$L$",(5,4),NE);
[/asy]
train