I'd like to use work estimates rather than duration estimates for project activities. How do I calculate how much extra to add for a risk buffer so that I can finish my projects on schedule?

A. Pad each task by 10-15 percent; more if it is a software development task.

B. Use the statistical probabilities calculated by automated software to choose your buffer.

C. Take the risk buffer from your last project and add your birthday.

D. Multiply duration estimates by two to arrive at work estimates.