write my assignment 4390

Can someone help me figure out how to work problem in excel? I have worked out the math I just cannot figure out how to input it into excel.Input it into excel.

A metropolitan school system consists of three districts-north, south, and central. The north district contains 25% of all students, the south district contains 40%, and the central district contains 35%. A minimum-competency test was given to all students; 10% of the north district students failed, 15% of the south district students failed, and 5% of the central students failed.

a. Develop a probability tree showing all marginal, and joint probabilities.

b. Develop a joint probability table.

c. What is the probability that a student selected at random failed the test?