Counting Book Selections by Four Students with a Total Cap

Company: ZS Associates

Difficulty: medium

Problem Statement

Question 1

At a library, four students choose books independently. Let A, B, C, and D denote the numbers of books chosen by the four students, where each number can be zero or more. If the total number of books chosen is at most 10, how many possible selections (A, B, C, D) are there?