Final answer:
The grade of the ore body cannot be determined based on the given information.
Step-by-step explanation:
The grade of the ore body is the amount of valuable mineral or metal that is found in the ore. In this case, the ore is fells rock and the valuable mineral is silver. The question states that one cubic meter of fells rock contains 540 grams of silver. To calculate the grade, we divide the mass of silver by the mass of the ore body and multiply by 100.
Grade of ore body = (mass of silver / mass of ore body) * 100
Grade = (540 g / mass of ore body) * 100
Unfortunately, the question does not provide the mass of the ore body, so we cannot determine the grade of the ore body based on the given information.