Solve the Problem $400 \mathrm{ft}$ After 40 Minutes the Bell Is at a Depth

Solve the problem. Round your answer, as needed.
-A deep sea diving bell is being lowered at a constant rate. After 12 minutes, the bell is at a depth of $400 \mathrm{ft}$ . After 40 minutes the bell is at a depth of $2000 \mathrm{ft}$ . What is the average rate of lowering per minute?

A) $0.02 \mathrm{ft}$ per minute
B) $40.0 \mathrm{ft}$ per minute
C) $57.1 \mathrm{ft}$ per minute
D) $50.0 \mathrm{ft}$ per minute