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The larger rectangle has dimensions 12 + 2*2 = 16 ft (width) and 17+2*2 = 21 ft (length).
The area of the concrete border is 16*21 - 12*17 = 132 square feet.
Solved.
Notice that the info about "A circular grassy region with a 96 ft diameter" is excessive, unnecessary and is not used in the solution of this problem.