(2)
where, c is the constant of integration Note that when t = 0, y = 250 Therefore, 250 = 200 + C
or
C = 50
Then (2) reduces to
y = 200 + 50 
40
t
e
− (3)
or
200
50
y−
 = 
40
t
e
−
or
40
t
e
 = 
50
200
y−
Therefore
t = 40
50
200
loge
y −
