Runners at a cross-country meet run 2 miles south and then 4 miles west from the starting

Runners at a cross-country meet run 2 miles south and then 4 miles west from the starting line. determine the shortest straight path they must run to get back to the starting line.
a. 6 miles square
b. root of 6 miles
c. square root of 12 miles
d. square root of 20 miles