Use a Formula for Perimeter or Area to Solve the Problem

Multiple Choice

Use a formula for perimeter or area to solve the problem.
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Find the area of the triangle.

A) $120 \mathrm {~km} ^ { 2 }$
B) $68 \mathrm {~km} ^ { 2 }$
C) $60 \mathrm {~km} ^ { 2 }$
D) $40 \mathrm {~km} ^ { 2 }$