After grading a lot, a builder places four stakes to designate the corners of the slab for

Question:

After grading a lot, a builder places four stakes to designate the corners of the slab for a house. To provide a firm, level base for the slab, the builder places a minimum of 60 mm of gravel beneath the slab. Determine the volume of gravel needed and the x coordinate of the centroid of the volume of the gravel. (Hint: The bottom of the gravel is an oblique plane, which can be represented by the equation y = a + bx + cz)

72m 60 uma 12m 100 n 120 mn| 160 mm