In an after school program, students must choose to either play on the playground or read a book silently. on one cloudy day, 70% of the students chose to play on the playground, and the rest chose read a book silently. 60% of the students who went to the playground are boys, and 20% who stayed inside to read a book are boys. if a student is randomly selected on this day, what is the probability that the student is a girl