1.   6 x 8 x 1 = $40
2.   5 x 7 x 1 = $40
3.   4 x 6 x 1 = $35
4.   3 x 5 x 1 = $30
5.   3 x 4 x 1 = $30
6.   3 x 3 x 1 = $30

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If you rent all six = $205