The first digit of a randomly chosen expense account claim

Question

Question: The first digit of a randomly chosen expense account claim follows Benford's law. Consider the events A = first digit is 7 or greater and B = first digit is odd.

(a) What outcomes make up the event A? What is P(A)?

(b) What outcomes make up the event B? What is P(B)?

(c) What outcomes make up the event "A or B"? What is P(A or B)? Why is this probability not equal to P(A) + P(B)?