Answer:
$1.944 million
Step-by-step explanation:
dQ/dt = k(100-t)²
Q = -k(100-t)³/3 + c
t = 100, Q = 0
t = 0, Q = 9000000
0 = -k(100-100)³/3 + c
So c = 0
Q = -k(100-t)³/3
9000000 × 3 = -k(100)³
27000000 = -1000000k
k = -27
Q = 27(100-t)³/3
Q = 9(100-t)³
t = 40
Q = 9(60)³
Q = $1944000
Q = $1.944 million