Beginning Balance: x

Period Contribution: y

Annual Contributions: 26

Years: 5

Annual Interest: 4% (compounded monthly)

*You can not earn interest on contributions during the current month.

I want to know how long it will take to accumulate $100,000 based on x beginning balance and y contributions by having a formula, but I cannot figure it out .

Below indicates the number of contributions per month for 2017-2021

THANK YOU