During proofing of the product manual, a problem was discovered requiring 15 days additional time...

To maintain the product availability date while accommodating a 15-day delay in proofing corrections, the best course of action is to expedite another activity on the critical path. The PSP Study Guide outlines methods for schedule recovery and acceleration (Section 2.3.5, "Acceleration"). Expediting the Draft Product Manual by 5 days helps redistribute the time lost, aligning subsequent tasks to achieve the original completion milestone without delaying the overall schedule.