Dan owns a car and a bicycle. He uses the car 30% of the time to travel to the university and the bicycle 70% of the time. When he uses the car, he makes it to school in at most 15 minutes 65% of the time, whereas if he bikes. He makes it to school in at most 15 minutes 90% of the time. Given that he made it to school in at most 15 minutes, what is the probability that he had used the bikes?
