Please show calculations so I can understand how to solve these types of problems.

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. b. What is the probability that the project can be completed in 24 days or less? In 21 days or less? (Round your te and z values to 2 decimal places and "Standard deviation" to 3 decimal places. Round your final answers to 4 decimal places.) c. Suppose it is now the end of the seventh day and that activities A and B have been completed while activity D is 50 percent completed. Time estimates for the completion of activity D are 5,6 , and 7 . Activities C and H are ready to begin. Determine the probability of finishing the project by day 24 and the probability of finishing by day 21. (Round your intermediate calculations to 3 decimal places and final answers to 4 decimal places.)