Jessica and Monte sell bananas at a produce stand. Jessica earns $4 for each crate of bananas she sells. At the end of the week, Monte has earned $15 less than Jessica. The following expression shows Monte's earnings:

4y − 15

In the expression, what does the first term represent?

Jessica's earnings at the end of the week
The number of crates of bananas Jessica sold
Monte's earnings at the end of the week
The number of crates of bananas Monte sold