A picnic shelter in a park will cover a square region 30 ft. by 30 ft. (900 square ft.). The park has dimensions 60 ft. by 150 ft. If you want to build the picnic shelter using only a portion of the this space, 40 ft. by 130 ft., how many different locations in the park are possible for the placement of the picnic shelter?

There is an accompanying small sketch with the problem: 1 rectangle that is 60 x 150 and the bordering edge along each side of the rectangle is shaded (the area the you cannot build the shelter in) and the 2nd rectangle (unshaded) within the the first rectangle.

I'm not sure how to obtain the answer which is 22.