a doctor wants to visit a patient.frpm the past experience,it is known that the probabilities that he will come by train,bus,scooter or by other means are 3/10,1/5,1/10,2/5.the probabilities of coming late are 1/4,1/3,1/12 if he comes by train,bus and scooter respectively,but if he comes by other means of transport then he will not be late.when he arrives he is late.what is the probability that he comes by train?