probability problem

three class 4a,4b and 4c attend a quiz contest. Three representatives from each class will answer 10 questions. If any representative answers a question correctly, the class will get 10 marks, otherwise they will get no marks. the probability that each of the representatives can anser a question correctly are 0.6, 0.8 and 0.75 respectively.a)find the probability that the representative of 4C will give a correct answer to aquestion.b)given that 4A and 4B got 80 and 60 marks respectively after answering the questions, find the probability that 4C will win the contest, correct to 4 dec. place.