Final answer:
The question seeks to determine the correct box volume for electrical components but lacks necessary details for a complete answer. Calculations would usually be based on the NEC's volume allowances which are not provided.
Step-by-step explanation:
The question asks for the volume of an electrical box required to house an SPST switch, two three-wire #14 AWG NMD90 cables, and four insulated splice caps. The calculation of the box volume is a topic in electrical engineering, which is often covered in vocational or technical classes that involve understanding electrical code requirements.
Unfortunately, the question does not provide the necessary information such as the volume allowances specified in the National Electrical Code (NEC) for conductors and devices to fully answer it. Generally, each conductor, splice cap, and device within a box is allocated a specific volume in cubic inches according to the NEC. To answer the question, one would add up all those individual space requirements and match it to the nearest larger standard box size. Without the specific values from the NEC, an exact answer can't be provided.
Additionally, the information provided in the reference section is irrelevant to the question and appears to be electrical formulas pertaining to energy (U = C V^2), resistance (Req), voltage (V), and power (P), but these are not related to calculating box volume for electrical installations.