What is the gradient of the graph shown? Give your answer in its simplest form.

Iam so stuck. what is the worked out answer for this question?

List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6

What is the product? a-3/15a × 5/a-3