The scenario describes a situation where the leaf-raker earns an initial payment of $10, and then earns an additional $15 for every hour worked.
The total earnings can be expressed as:
\[ \text{Total Earnings} = 10 + 15h \]
where \( h \) represents the number of hours worked.
This equation is a linear function because it represents a constant rate of change (earning $15 for each additional hour worked).
Therefore, the best response is:
a positive linear function.