Need help with this question. I think I got question a right so far, but having trouble with question b. Please help me with and explain the formula for b.

(a) Neil opened his piggy bank and found that he had 17 pennies. He lined them all up on the floor. Katie came along and replaced every second coin with a nickel. Next, Pratima replaced every third coin with a dime. Finally, Chad replaced every fourth coin with a quarter. How much money does Neil now have?

Pennies = 6: 0.06

Nickel = 3: 0.15

Dime = 4: 0.40

Quarter = 4: $1.00

1.00 + 0.40 +0.15 + 0.06 = $1.61

Therefore Neil has $1.61.

(b) How much money would Neil have if he started with 2021 pennies? (The same rules apply.)