Solve Questions using Data Provided:

5. (10) From Steps 3 and 4 determine the Probable Life Curve by determining the area under the curve for each selected age (remember you need to compute the area to the right of the selected age to get the y-axis value for percent survival). As mentioned in problem 4 if software use becomes a problem then it can be graphed on a tight grid with most electronic graphing software and an estimate of the areas under the curve determined manually by counting the grids (e.g., 10 x 10 = 100 area units).

6. (10) Using the Probable Life Curve, determine when the remaining Manholes in the original data set will need replacement and determine the net present value of those replacements in year 2020 dollars. Manhole replacement has an estimated constant future cost of $25,000 for each manhole at the end of its life. For planning purposes set the interest rate to 3% in your engineering economic calculations.