Margot is looking at some information for the obstacle course she is interested in completing. The x-coordinate is the number of the obstacle, while the y-coordinate is the average time to complete the obstacle, measured in minutes. (1, 6.25), (2, 6.875), (3, 7.5625), (4, 8.31875)

Help Margot use an explicit formula to find the average time she will need for the 8th obstacle.

f(8) = 1.1(6.25)7; f(8) = 409782
f(8) = 6.25(1.1)7; f(8) = 12.179
f(8) = 1.1(6.25)8; f(8) = 2561137
f(8) = 6.25(1.1)8; f(8) = 13.397