Describe how you can use a formula to solve the following problem: The inner edges of a cube-shaped pot have a length of 1.5 feet. How much does it cost to fill the planter if soil costs $4 per cubic foot?

Creating a formula:

Let a be the length of each edge of the pot (area of a cube = a^{3})

Let c be cost per cubic foot

Cost to fill = a^{3} * c

1.5^{3} = 3.375 cubic feet

1.5^{3} * 4 = $13.50 to fill the planter