If the pattern below follows the rule "starting with four, every consecutive line has a number one more than the previous line," how many marbles must be in the seventh line?

Melanie is buying a bathing suit that costs 39.99. she is given a discount at the cash register of $6.00 when she scratched 15% off on a game piece for a store promotion. what will the sale price of melanie’s bathing suit be?