Answer:
$318.17, out of state college is $161.12 cheaper per month
Explanation:
72*24 = 1728 + 410*4 = 1728 + 1640 = 3368 + 450 = 18/12 = $318.17
8700+650*9 = 8700 + 5850 = 14550/9 = 1616.66
8500+400*9 = 8500 + 3600 = 12100 + 1000 = 13100/9 = 1455.56
1616.67 - 1455.56= $161.11 (use $161.12)