6.) A ball is thrown upward with initial velocity of 64 feet per second from an initial height of 80 feet. (Assume the acceleration is a(t) per second). ( hint: initial condition: s(0) = 80 , s'(0) = 64) (a) Find the position function giving the height s as a function of time t. (b) When does the ball hit the ground ? For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac)