4. In an exam hall, one row has 20 seats. The GSI randomly permutes 20 students into those 20 seats. a) Students A and B are among the 20 students in the row. Find the decimal value of the expected number of students sitting between them. b) The 20 students in the row include 7 Data Science majors. Find the expected number of Data Science majors who are not seated next to another Data Science major. You don't have to find the decimal value