Ice forms on a refrigerator icebox at the rate of (4 – 06t)g per minute after t minutes. If initially there are 2g of ice in the box, find the mass of ice formed in 5 minutes

A.
19.5 
B.
17.0 
C.
14.5 
D.
12.5
Correct Answer: Option C
Explanation
(frac{dm}{dt}) = 4 – 0.6t
(int)dm = (int)(4 – 0.6t)dt
m = (4t – 0.3t^2 + c), when t = 0, m = 2g
∴ c = 2
m = (4t – 0.3t^2 + 2), when t = 5 minutes
m = (4(5) – 0.3(5)^2 + 2 = 20 – 7.5 + 2)
= 14.5