In a water-tank test involving the launching of a small model boat, the models initial horizontal velocity

Question:

In a water-tank test involving the launching of a small model boat, the model’s initial horizontal velocity is 20 ft/s and its horizontal acceleration varies linearly from − 40 ft/s2 at t = 0 to − 6 ft/s2 at t = t1 and then remains equal to −6 ft/s2 until t = 1.4 s. Knowing that v = 6 ft/s when t = t1, determine
(a) The value of t1,
(b) The velocity and position of the model at t = 1.4 s.