A zoo needs to transport their monkeys to the vet either by bus or by car. A bus can transport 20 monkeys per trip and takes 30 minutes. A car can transport 6 monkeys per trip and takes 15 minutes. There can be at most 10 bus trips. In addition, since the monkeys get aggressive when there are too many in one place at least 60% of the trips should be by car. If the zoo needs to transport 300 monkeys, how many trips of each should be done to minimize the total time required to transport the monkeys?