To calculate the volume of a right rectangular prism, you can use the formula:
\[ \text{Volume} = \text{Base Area} \times \text{Height} \]
In this case, the base area is given as 15 square inches, and the height is 5 inches.
So, the volume can be calculated as follows:
\[ \text{Volume} = 15 , \text{in}^2 \times 5 , \text{in} \] \[ \text{Volume} = 75 , \text{in}^3 \]
The volume of the gift box will be 75 cubic inches.