Miguel is driving his motorboat across a river. The speed of the boat in still water is 13 mi/h. The river flows directly south at 5 mi/h. If Miguel heads directly west, what are the boat’s resultant speed and direction? (Not drawn to scale)
a. 21 mi/h; 13.9 north of west
b. 13.9 mi/h; 21 south of west
c. 13.9 mi/h; 21 north of west
d. 21 mi/h; 13.9 south of west