I'm no longer fluent in math but retain some ability in algebra after all these years...

Still, I'm having trouble setting up a problem from a puzzle calendar that a friend gave me. It seems like a piece is missing, although I'm not entirely convinced that's true. Here's the quote:

Rachel wanted to buy some tiny favors for a Mardi Gras party. She tried to drive a hard bargain and succeeded. If she had paid $0.04 more per hundred, she would have received five fewer. How much did the favors cost per hundred?

Any hints or suggestions, or other comments? Thank you!

Glipto

x = cost per hundred
y = units
M = Rachel's money

M = x /100 * y
or M = (x + 0.04)/100 * (y - 5)

xy = (x +0.04) * (y - 5)

...

y = 125 * x + 5 (many solutions)

M value is missing.