4. A bat exerts a horizontal force F(t) = (1.6 x 10^7 N/s^2) t - (6.00 x 10^9 N/s^2) t^2] u "x", where u "x" = (1,0,0) = i, on a 0.145 kg ball between initial t = t0 and final t = 2.5 ms. At t0 = 0s, the ball speed is equal to (-40.0u "x" + 5.0u "y") m/s, where u "y" = (0,1,0) = j. (a) Calculate the momentum of the bat on the ball during the 2.5 ms that are in contact. (b) Calculate the momentum exerted by gravity on the ball during that time. (c) Calculate the "average force" exerted by the bat during that period of time. (d) Calculate the "momentum" and the speed of the ball at t = 2.5 ms.