Hello there. To solve this question, we'll need to remember some properties about triangles.
First, the area of a right triangle as in the following drawing:
Can be calculated by the formula:
If the area of the enclosed triangular region is greater than or equal to 60, we have the following inequality;
Now, using the lengths of the sides of the triangle, we'll have:
Therefore
Divide both sides of the inequality by a factor of 6
The least possible value of c is 10 ft.