In our class, 1/8 of the students take public transport to school, 25% are driven by their parents, and the remaining 20 students walk to school. How many students are there in our class

Fracisco's game involves 3 green, 2 yellow, 4 red, and 3 black marbles. if he randomly draws three marbles from the bag, without replacement, what is the probability that he will draw yellow, and then red, and then black? a)1/192 b)1/72 c)3/220 d)1/55