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Estimate ffR($ 3y2)dA R: [0,2] x [1,2] = {($,y) :0 S a: 5 2,1 5 y S 2} a) Divide R into four equal subrectangles by the dividing the intervals [0,2], and [1,2], in half, and constructing rectangles from these divisions in the obvious way. Then, to carry out your estimate, let the sample point in each rectangle be its upper-right corner. b) Repeat the previous exercise. This time letting the sample points be the lower-left corner of each sub-rectangle. c) Repeat the previous exercise. This time letting the sample points he the center of each subrectangle. This is called the Midpoint Rule, akin to the rule of the same name for singlevariable functions)