2011 AMC 10A Problems/Problem 9

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A rectangular region is bounded by the graphs of the equations y=a, y=-b, x=-c, and x=d, where a,b,c, and d are all positive numbers. Which of the following represents the area of this region?

We have a rectangle of side lengths $(a - -b)$ and $(d - -c)$ Thus the area of this rectangle is $(a + b)(c + d) = ac + ad + bc + bd$