The excursion boat on the river takes 2 hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate of the river current

The excursion boat on the river takes 2 hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate of the river current, what is the rate of the current? Which of the following equations can be used to solve for c, the rate of the current?

(4c)(2.5) + (6c)(2.5) = 24

(4c)(12) + (6c)(12) = 2.5

[12/(4c)] + [12/(6c)] = 2.5