21. You are a project manager overseeing the construction of a Baseball Stadium. The activity of laying the Grass Sod has an optimistic estimate of 10 days, pessimistic estimate of 16 days, and most likely estimate of 13 days. If your company has a quality requirement of Six Sigma, what is the duration within which this task must be completed?

a) 1dayto6days

b) 7 days to 19 days

c) 22 days to 24 days

d) 10 days to 12 days