Answer:
d. 126; 70
Explanation:
given that Ron finds 9 books at a bookstore that he would like to buy, but he can afford only 5 of them.
Out of 9 books he has to select 5 of them
Here selection of books can be done in any order. Hence order does not matter
No of ways he selects 5 books out of 9 books = 9C5
= 126
Part II
One book is a must
Hence he has options only 4 books from the remaining 8.
No of ways when one book is compulsory = selecting 3 books from 8 books
= 8C4
= 70
Option d is right.