The scenario that can be modeled by a linear function is:
The total cost of building a new home if the builder charges $300 per square foot.
This situation represents a linear relationship because the total cost is directly proportional to the number of square feet. If \( x \) is the number of square feet, the total cost \( C \) can be expressed as:
\[ C = 300x \]
where \( 300 \) is the constant rate charged per square foot. All other scenarios involve variables that do not provide a consistent linear relationship.