Please help :(

A tennis ball is thrown into the air with velocity 56 feet per second. It's height in feet t seconds later is given by f(t)=56t-16t^2

A.) find the average velocity for the time period beginning when t=2 seconds and lasting....
i. 0.5 seconds. ii. 0.1
iii. 0.05. iv. 0.01

B.) using your work in part a, estimate the instantaneous velocity when t=2

Question

Please help :( 

A tennis ball is thrown into the air with velocity 56 feet per second. It's height in feet t seconds later is given by f(t)=56t-16t^2

A.) find the average velocity for the time period beginning when t=2 seconds and lasting.... 
   i. 0.5 seconds.                  ii. 0.1
   iii. 0.05.                             iv. 0.01

B.) using your work in part a, estimate the instantaneous velocity when t=2