Given a bigger rectangle with dimensions 14 feet by 15 feet and a smaller rectangle with dimensions (15 - 4) feet by (14 - 6) feet (i.e. 11 feet by 8 feet) inside the bigger rectangle.
The preimeter of a figure is the total length of the external outline of the figure.
Here, the perimeter of the unshaded portion of the figure is the sum of the external outline of the given figure.
Therefore, the perimeter is given by 14 + 4 + (14 - 6) + (15 - 4) + 6 + 15 = 18 + 8 + 11 + 21 = 58 feet.