The price of a gym membership has a one-time sign-up fee and a monthly fee. The price can be modeled by the function y = 10x + 15, where x is the number of months.

What is the y-intercept, and what does it represent? (1 point)

10; it represents the monthly fee

10; it represents the one-time sign-up fee

15; it represents the monthly fee

15; it represents the one-time sign-up fee