A book publisher has noted that, on average, one page in eight contains at least one spelling error, one page in five contains at least one punctuation error, and that these errors occur independently and at random. The publisher checks 480 randomly selected pages from various books for errors.

a. How many pages are expected to contain at least one of both types of error?

b. Find the probability that:

i. The first spelling error occurs after the 10th page

ii. The first punctuation error occurs before the 10th page

iii. The 10th page is the first to contain both types of error.