The relationship between the total amount spent on food and drinks by the customers that a waiter serves at a restaurant during a particular week and the waiter's total income for that week can be modeled by the equation y = 0.2x + 300, where x is the amount spent by the customers in dollars and y is the waiter's total income in dollars. By how much does the waiter's weekly income increase for every $500 spent by his customers during that week? A
$100

B
$300

C
$400

D
$500