Using the PERT three$-$estimate approach, the three estimates for one of the activities of a project are as follows: optimistic estimate $=30$ days, most likely estimate $=36$ days, pessimistic estimate $=48$ days. What are the resulting estimates of the mean and variance of the duration of the activity?

Mean: $[$ Select $]["42","37","34","36"]$

Variance: $[$ Select $]["12","9","13","3"]$