Q4Please help

Question 4 A pitcher's mound is 18 metres from the home plate where the batter is preparing for the delivery of the ball. Suppose that the function that describes the distance the ball has travelled is s(t) - --6t- + 24t, where t is the time from the pitcher's release to the batter's contact in seconds and's is in metres. a) Find the time in which the ball reaches the batter. b) Find the velocity of the ball at time t by using the limit definition of the derivative c) Solve for the velocity of the ball when it reaches the batter