How do I calculate this?

Q5. We know that Stephen has a-80% chance to be active in 2018, and the yearly retention rate is 90% (i.e., the likelihood to be active in the next year given a customer is active in a particular year is 90%). What is the likelihood that Stephen will still be active at the end of the 2020 (Choose the closest number) ? (A) 80% (B) 75% (C) 70% (D) 65%