fake gold bricks are made by covering concrete cubes with gold paint, so the cost of the paint is directly proportional to their surface area while the cost of the concrete is directly proportional to their volume. a cube with edges of length $1$ inch costs $\$1.30$ to make, while a cube with edges of length $2$ inches costs $\$6.80$ to make. how much would a cube with edges of length $3$ inches cost to make?