A skydiver: If a skydiver jumps from an airplane, his velocity v, in feet per second, starts at 0 and increases toward terminal velocity. An average-size man has a terminal velocity T of about 176...

A skydiver: If a skydiver jumps from an airplane, his velocity v, in feet per second, starts at 0 and increases toward terminal velocity. An average-size man has a terminal velocity T of about 176 feet per second. The difference D = T − v is an exponential function of time.

a. What is the initial value of D?

b. Two seconds into the fall, the velocity is 54.75 feet per second. Find an exponential formula for D.

 c. Find a formula for v.

d. Express using functional notation the velocity 4 seconds into the fall, and then calculate that value.