Please help for a brainlist ;)) Determine the written expression that would model

Please help for a brainlist ;)) Determine the written expression that would model the given equation:

y=20x+50

Question options:

A. Sally joins a gym. Her initial membership fee is $50 and she pays $20 for each month that she is a member.

B. Jackson purchased a cell phone for $20. For each month, he pays $50 for the cell phone service.