Answer:
$400.27
Explanation:
owes $424.04
returns an item for $49.95
-424.04 + 49.95 = -374.09
he now owes $374.09
returns an item for $50.42
-374.09 + 50.42 = -323.67
he now owes $323.67
makes a purchase of $39.19
-323.67 - 39.19 = -362.86
he now owes $362.86
makes a purchase of $37.41
-362.86 - 37.41 = -400.27
he now owes $400.27