can you briefly explain?

4. The following table shows the probability distribution for the number of books a student typically buys at the annual book fair held at an elementary school Number of Books 0 1 2 3 5 6 7 Probability 0.35 0.20 0.15 0.10 0.07 0.08 0.04 0.01 Let the random variable B represent the number of books a student buys at the next book fair. What is the expected value of B ? Copyright O 2020. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school's participation in the program is prohibited. Page 2 of 9 AP CollegeBoard AP Statistics Test Booklet Unit 4 SA A) B 1.00 C 1.79 D 3.50 E 28