Coal is mined in two seams that are shown in the sketch. Mining is full seam height in both seams. Entries are 24 ft wide (7.3 m).With reference to the stratigraphic column and rock properties in the sketch, determine for the lower seam:
(a) The safety factor with respect to tension of the immediate roof layer over the entries, and
(b) The second roof layer,
(c) A reasonable bolting plan using the dead weight load approach. Include (i) bolt length, (ii) nominal diameter, (iii) steel grade, and (iv)spacing.