A Ph.D. class has three students in it: Alice, Bob and Chris. When I ask a question in that class, someone always answers. Alice is the first one to answer twice as often as Bob and half as often as Chris. When they answer my questions in class, Alice gets it right 80% of the time; Bob, 70% of the time and Chris, 60% of the time. If I ask a single question, how likely is it that the first answer will be correct?