A project consists of three activities that need to be completed sequentially. $($A$,$ then B$,$ then C$).$

Assume the three activity times are normally distributed and mutually independent. The mean, standard deviation, and variance of the three activity times are shown below.

times

Let TA be the amount of time required to complete activity A$,$ TB the time required to complete activity B$,$ and TC the time required to complete activity C$.$ If the individual activity start times are flexible $($don$\text{'}$t need to be scheduled or known in advance$)$ then the time to complete the project is TA $+$ TB $+$ TC$.$

Under this assumption, what is the mean project duration? $($What is the average value of TA $+$ TB $+$ TC $?$ Do not round your answer. It is an average value.$)$