Please help

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?

36x2 + 49y2 = 1,764 the foci are located at: (-√13, 0) and (√13,0) (0, -√13) and (0,√13) (-1, 0) and (1, 0)edit: the answer is (- the square root of 13, 0) and (the square root of 13, 0)

Find the distance between c and d on the number line c=3 and d=11