Consider the region below (x) = x/2, above the x-axis, and between x = 0 and x

Consider the region below ƒ(x) = x/2, above the x-axis, and between x = 0 and x = 4. Let x_i be the midpoint of the ith subinterval.

(a) Approximate the area of the region using four rectangles.
(b) Find ∫₀⁴ ƒ(x) dx by using the formula for the area of a triangle.