Simple Monthly Recurring Revenue Q: Formula to know how much I made in 6 months?

I have a somewhat simple math formula I was wondering if I can get some help with.

- I get 5 customers per week. Each month has 4.3 weeks, so I get about 21.5 customers per month.
- Customers pay $10 per month in a subscription service.
- In 6 months, how much revenue would I have made?

I think this has to do with "compounding revenue", thought I'm not completely sure what the math term for it is. The reason I find it tricky is this:

- In month 1, if I get 21.5 customers paying $10/month, that's $215.00.
- In month 2, I would have double the customers, which is $420 for that month. If I add the $215 from the first month, that's $635 revenue total.

I'd like to be able to input the number of months in a Cell, and then have the total calculated in another cell. Any help would be appreciated, thanks!