If $$t_o, t_p $$ and $$ t_m$$ are the optimistic, pessimistic and most likely time estimates of an activity respectively, then the expected time t of the activity will be : 

A

$$\frac{t_o + t_p + t_m}{3}$$

B

$$\frac{t_o + t_p + 3t_m}{5}$$

C

$$\frac{t_o + t_p + 2t_m}{4}$$

D

$$\frac{t_o + t_p + 4t_m}{6}$$