4. A bicycle is ridden down the Hudson River bike path for one hour, with speeds mea sured at 10minute intervals as follows. Time (min) 10 20 30 40 50 60 (a) Estimate the total distance traveled using the speeds at the beginnings of these intervals. (b) Estimate the total distance traveled using the speeds at the ends of these intervals. (c) How are these estimates related to Riemann sums? Explain