A ball is tossed straight up into the air from a bridge,and its height above the ground t seconds after it is thrown is

f(t)=-16t^2 + 108t + 82 feet.

a.How high above the ground is the bridge?

b. Write a function A(b) that gives the average velocity of the ball from t=0 to t=b seconds.Use the function to calculate the average velocity of the ball the first two seconds it is in the air.