SAT Math Practice Question

A painter will paint $n$ walls with the same size and shape in a building using a specific brand of paint. The painter's fee can be calculated by the expression $n K \ell h$, where $n$ is the number of walls, $K$ is a constant with units of dollars per square foot, $\ell$ is the length of each wall in feet, and $h$ is the height of each wall in feet. If the customer asks the painter to use a more expensive brand of paint, which of the factors in the expression would change?

1. A.$h$
2. B.$\ell$
3. C.$K$
4. D.$n$