A projectile enters a resisting medium a X= 0 with a initial velocity of Vo = 900 ft/s and travels 4 in. before coming to rest. Assuming that the velocity of the projectile is defined by the relation,V=Vo - kx where is expressed in ft/s and a in feet. Determine (a) the initial acceleration of the projectile, (b) the time required for the projectile to penetrate 3.9 in. in the resisting medium.