I need help on this question

In this problem, use the general expressions for left and right sums, left-hand sum = f(to) At + f(t, ) At + .. . + f(t, 1)At and right-hand sum = f(t,)At + f(t2) At + .. . + f(tn)At, and the following table t 0 5 10 15 20 f (t) 21 19 17 13 12 A. If we use n = 4 subdivisions, fill in the values At - to = .+1 =t2 - ts = t4 = f (to) = f (t1) = f (t2) f (ts ) = f (ta ) = B. Find the left and right sums using n = 4 left sum = right sum = C. If we use n = 2 subdivisions, fill in the values: At = to = : t1 = t2 f (to ) = f (t1) = f(t2) = D. Find the left and right sums using n = 2 left sum = right sum =