We are asked to determine the mass of 19 gallons of gasoline. To do that we will use the following formula:

Where:

First, we will convert the slug to pounds using the following conversion factor:

Multiplying by the conversion factor we get:

Now, we will convert the gallons into cubic feet using the following conversion factor:

Multiplying by the conversion factor:

Now, we substitute in the formula for the mass:

Solving the operations:

Therefore, the mass is 936.8882 pounds.