solution

Table 12-1 Activities required to renew a pipeline ID Code Activity Days Immediate Predecessor Activities A. B. 10 28 2 D. E. F. G. H. I. J. K. L. M. N. Assemble crew for job Use old line to build inventory Measure and sketch old line Develop list of materials Erect scaffold Procure pipes Procure valves Deactivate old line Remove old pipe Prefab new pipe Place valves Place new pipe Weld pipe Connect values Insulate Pressure test Remove scaffold Clean up and turn over to operating crew 2 30 45 1 6 5 1 6 2 1 4 1 1 1 None None ? ? D D D B, D H, E F E, G, H I, J L K, M K, M N NO P, Q P. R.