The johnsons want to cover their backyard with new grass. their backyard is rectangular, with a length of 3x - 5 feet and a width of 4x - 10 feet. however, their rectangular swimming pool, along with its surrounding patio, has a dimension of x + 8 by x - 2 feet. what is the area of the region of the yard that they want to cover with new grass?

a. x^2 + 6x - 16 ft^2

b. 6x^2 - 55x + 104 ft^2

c. 12x^2 - 50x + 50 ft^2

d. 11x^2 - 56x + 66 ft^2