Kerri P. answered 01/12/20
Patient and Experienced Math Tutor Specializing in Calculus
To me, this seems like a Riemann Sum problem. Usually finding the left- and right-hand Riemann sums will give you known under- and over-estimations, based on whether the function is increasing or decreasing. Since the function we are given is both increasing and decreasing, from the points in the table, I am not completely sure if they want you to do kind of a modified version, but that's what I will propose. (The question is a little vague, I mean we could say 10 million cars for our over-estimate and 2 cars for the under-estimate based on these directions!)
My proposal: For the overestimate, use the right-hand Riemann sum for the first 3 months and then the left-hand sum for the last 3 months. Switch it around for the underestimate.
A. over = 1200 cars, under = 800 cars
B. over = 1200 + 1600 + 1900 + 1900 + 1600 + 1500 = 9700 cars
under = 800 + 1200 + 1600 + 1600 + 1500 + 1300 = 8000 cars
I could have completely misinterpreted the problem, but this is what I would do!