The areas of a rectangular painting is 12x²+11x-15 square feet. Which of the following could be the dimensions of the painting?
a. (4x-3) feet by (3x+5) feet
b. (4x+3) feet by (3x-5) feet
c. (12x-3) feet by (x+5) feet
d. (6x-5) feet by (2x+3) feet