You are the project manager of a project. While reviewing the cost estimates for the project, you notice that one of the cost estimates for a WBS item is 20% higher

Please discuss the following:

You are the project manager of a project. While reviewing the cost estimates for the project, you notice that one of the cost estimates for a WBS item is 20% higher than previous projects for very similar work. What should you do next?
Together with your team, you have applied three-point estimation to a critical path consisting of two activities. The following duration uncertainties are calculated assuming a confidence interval of ±3 sigma. The duration uncertainty -defined as the pessimistic estimate minus the optimistic one- of the first activity is 18 days; the second estimate has an uncertainty of 24 days. Applying the PERT formula, what is the duration uncertainty of the entire path?
Your project has exceeded costs in the past due to underestimation of resource costs at the cost baseline: PV: $1,200,000, EV: $1,000,000, AC: $1,200,000. You expect underestimation to influence the future as much as it did in the past. If the BTC (Budget to Complete) is $1,000,000, what should your new EAC (Estimate at Completion) be?