Task F

You have to find the critical path and then figure out what task is not on the critical path and use the formula for float.

PMP does not ask any such tranasforming questions.

AOA - can indicate Float in some cases , and only such questionins,are given in few mock test . I never expect AOA based question are asked in PMP though uploaded example  or such any example are easy to answer.

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Tranforming is not easy. It require little higher practice and understanding. I can give you few hints:

• Activities On Arrows  hence consider node to node an individual activity.
• break every node and put a line in between with an arrow showing F to S relationship.

These 2 hints are sufficient, later is all on little imagination and understanding, there is no such text book or litrature.

your example is similar to earlier one ( http://pmzilla.com/q-critical-path )  in shape. Only one activity duration has been reduced.