A project consists of three parallel paths with durations and variances of (10,4), (12,4) and (12,9) respectively. According to the standard PERT assumptions, the distribution of the project duration is
(a) Beta with mean 10 and standard deviation 2.
(b) Bet with mean 12 and standard deviation 2.
(c) Beta with mean 10 and standard deviation 3.
(d) Beta with mean 1 and standard deviation 3.