The Carter family and the Tran family each used their sprinklers last summer. The water output rate for the Carter family's sprinkler was 35 L per hour. The
water output rate for the Tran family's sprinkler was 15 L per hour. The families used their sprinklers for a combined total of 40 hours, resulting in a total water
output of 1100 L. How long was each sprinkler used?