A gap starts at 15 centimeters. Its rate of change g'(t), in centimeters per minute, is shown. t: 0, 2, 5, 8; g'(t): 1.5, -0.5, 2.0, -1.0. Use a left endpoint Riemann sum with P = {0, 2, 5, 8} to estimate the gap at t = 8.