A project for improving a billing process has the following precedence relationships and activity times: Activity Immediate Predecessor(s) A B C Activity Time (weeks) 2 10 7 12 9 4 D A B, C B E F D G 3 7 E F.G H a. Choose the correct network diagram below. O A. OB E S B B D G 10 10 Oc. OD. D IS B B 10 b. Calculate the slack for each activity. Which activities are on the critical path? Activity Activity Time (weeks) On critical path? Slack (weeks) A 2 B 10 V 7 D 12 V E 9 F 4 G 3 H 7