To find the volume of the right rectangular prism made up of 4 cubes, each with a side length of 15 inches, you can use the formula for the volume of a cube, which is:
\[ \text{Volume} = \text{side length}^3 \]
First, calculate the volume of one cube:
\[ \text{Volume of one cube} = 15 \text{ in} \times 15 \text{ in} \times 15 \text{ in} = 3375 \text{ cubic inches} \]
Since there are 4 cubes, the total volume of the right rectangular prism is:
\[ \text{Total volume} = 4 \times 3375 \text{ cubic inches} = 13500 \text{ cubic inches} \]
So, the volume of the right rectangular prism is 13500 cubic inches.
However, this doesn't match any options provided in the question. There appears to be a mismatch, possibly because the context or method to calculate the volume was not accurately aligned with the choices.
If the question intended a different calculation based on the fractions provided for dimensions of a rectangular cuboid that is not specified clearly, please recheck the prompt or any calculation instruction closely.
In any case, based on the 4 cube information provided, the answer remains 13500 cubic inches.