need help solving and figuring the steps out for this question.

Three recent college graduates have formed a partnership and have opened an advertising firm. Their first project consists of activities listed in the following table. Use Table B. TIME IN DAYS Activity Immediate Predecessor Pessimistic 7 11 Optimistic Most likely 6 8 6 8 12 6 6 5 5 D E F G H I End C D F B E, G, 1 15 9 7 7 5 & 4 Click here for the Excel Data Elle What is the probability that the project can be completed in 24 days or less? In 21 days or less? (Round your t, and a values to 2 decimal places and "Standard deviation" to 3 decimal places. Round your final answers to 4 decimal places.) Days Probability 24 days or less 21 days or less b. Suppose it is now the end of the seventh day and that activities A and B have been completed while activity is 50 netent