7.18 A contractor is required by a county planning department to submit anywhere from one to five forms (depending on the nature of the project)

in applying for a building permit. Let y be the number of forms required of the next applicant. The probability that y forms are required is known to be proportional to y; that is, p(y) 5 ky for y 5 1, . . . , 5.

a. What is the value of k? (Hint: o ps yd  1.)

b. What is the probability that at most three forms are required?

c. What is the probability that between two and four forms (inclusive) are required?

d. Could ps yd  y2y50 for y 5 1, 2, 3, 4, 5 be the probability distribution of y? Explain.