Let f(x) = x2, and compute the Riemann sum of f over the interval [6, 8], choosing the representative points to be the left endpoints of the subintervals and using the following number of subintervals (n).

(a) Two subintervals of equal length (n = 2)

(b) Five subintervals of equal length (n = 5)

(c) Ten subintervals of equal length (n = 10)

(d) Can you guess at the area of the region under the graph of f on the interval [6, 8]?