Charlie is re-landscaping his back yard and uses a coordinate plane to map the yard out. There is a pine tree located at (-5, 5); the edge of a shed is located at (-5, 1) and the edge of a sandbox is located at (2, 5). He plans to cover the triangular area formed by these three points with gravel. What area of the yard will be covered in gravel? Note: On the coordinate plane, each gridline represents 2 feet. 56 square feet

112 square feet

14 square feet

28 square feet