Question: TRAFFIC FLOW Opened in the late 1950s, the Central Artery in downtown Boston was designed to move 75,000 vehicles a day. The number of vehicles moved per day is approximated by the function
x = f(t) = 6.25t2 + 19.75t + 74.75 (0 ≤ t ≤ 5)
where x is measured in thousands and t in decades, with t = 0 corresponding to the beginning of 1959. Suppose the average speed of traffic flow in mph is given by
S = g(x) = -0.00075x2 + 67.5 (75 ≤ t ≤ 350)
where x has the same meaning as before. What was the rate of change of the average speed of traffic flow at the beginning of 1999? What was the average speed of traffic flow at that time?