The price of a community pool membership has a one-time sign-up fee and a monthly fee. The price can be modeled by the function y = 20x + 50, where x is the number of months. What is the slope, and what does it represent?
A 20; it represents the monthly fee
B 20; it represents the one-time sign-up fee
C 50; it represents the monthly fee
D 50; it represents the one-time sign-up fee