A gardener is mixing different types of soil for a large planter. The table shows the cost per pound and the weight per cubic foot for four soil additives:
| Additive | Weight per volume (lb/ft³) | Cost per pound ($) |
|---|---|---|
| Compost | 45 | $0.05 |
| Perlite | 7 | $0.30 |
| Vermiculite | 10 | $0.25 |
| Sand | 90 | $0.02 |
The equation gives the total cost, in dollars, of the additives used, where is the volume of compost in cubic feet and is the volume of perlite in cubic feet. If all four additives are used in the planter, which of the following is the best interpretation of the value in this equation?
The total volume of vermiculite and sand used.
The total cost of the compost and perlite used.
The total cost of the vermiculite and sand used.
The total cost of all four additives.
