The cost of the shorter and longer side of the rectangular pen is $19.25 and $31.50 respectively.
Perimeter = 2(length + width)
56 = 2(3x + x)
56 = 2(4x)
56 = 8x
x = 56/8
x = 7
So,
Width = x
= 7 feet
Length = 3x
= 3(7)
= 21 feet
Cost of material used for the shorter side = $2.75 × 7
= $19.25
Cost of material used for the longer side = $1.50 × 21
= $31.50
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