The expected values and variances of the completion times of the activities are listed here. Determine the expected value and variance of the completion time of the project.

activity 1 2 3 4

expected completion time(days) 18 12 27 8

variance 8 5 6 2

before the problem it says e(x1 + x2 + ..xk)

and v(x1+x2+..xk)

do I get E by calculating the average of the completion times?

and then plug it in the e(x1+...xk) ?where the x1s are each completion time?

thanks for any help