The distribution of the number of occurrences of the letter "a" on the pages of a book is found to be a normal distribution with a mean of 60 and a standard deviation of 15. if there are 600 pages in the book, what percentage of the time is "a" found 45 times or more on a page? a. 68% of the time b. 50% of the time c. 84% of the time d. 34% of the time