Randomly open a 300-page book, and mark a page. a. Given that at least one of the

Question:

Randomly open a 300-page book, and mark a page.
a. Given that at least one of the digits on the chosen page is a 5, find the probability that the page is 255.
b. Given that at least two of the digits on the chosen page are 5's, find the probability that the page is 255.