Suppose 50% of the students in school have a part time job. Among those who have a partime job, 20% of them need to work at least 20 hours per week. If you randomly select a student in school, what’s...

Suppose 50% of the students in school have a part time job. Among those who have a partime job, 20% of them need to work at least 20 hours per week. If you randomly select a student in school, what’s the probability that the student does not work or works less than 20 hours per week?