80% of the customers at Starbucks downtown State College are Penn State students, and the remaining 20% are not. Among students customers, 90% use credit cards as method of payment, and 70% ofnon-student customers do so.

1. Find the probability that the next customer is a student and uses a credit card .

2. Find the probability that the next customer uses a credit card

3. If the next customer uses a credit card, find the probability that he/she is a student.