The charge of one late fee is -$10.
Given that,
- The total late fee was -$40.
- There are four late fees.
We need to find out the charge of one late fee.
So, the following formula should be used
\(= \frac{Total\ late\ fees}{number\ of\ late\ fees} \\\\= \frac{-\$40}{4}\)
= -$10
Therefore we can conclude that the charge of one late fee is -$10.
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