Final answer:
The correct dimensions for a 4-inch dirt pocket, based on the newer guidance, should be a length of about 24 inches to 30 inches and the diameter should remain as specified in the question, which is 4 inches. This corresponds to the option (c).
Step-by-step explanation:
The question pertains to determining the appropriate length and diameter of a dirt pocket with a specified measurement. The reference to a 'rule of thumb' suggests that the dimensions of the pocket should be proportionate to its diameter, likely following the guidance of an older rule or a more current recommendation contained in construction or engineering practices.
Given the traditional rule states that the dimensions should be 5 diameters side-to-side and 7-8 diameters deep, and newer guidance suggests up to 8 diameters side-to-side and 15 diameters deep, the correct dimensions for a 4" diameter pocket would be:
-Length: 4" times 15 = 60" (or 5 feet), which is about 24 inches to 30 inches.
-Diameter: 4", as specified in the question. Therefore, the correct answer would be c. Length: About 24 inches to 30 inches, Diameter: Roughly 10 inches to 12 inches.