The deck of a bridge is suspended 245 feet above a river. If a pebble falls off the side of the bridge, the height, in feet of the pebble above the water surface after t seconds is given by y=245-16t^2

A) Find the average velocity(in ft/s) of the pebble for the time period beginning when t=3 and and lasting 0.1 seconds and 0.05 seconds.

B) estimate the instantaneous velocity (in ft/s) of the pebble after 3 seconds