Probability2

At a school sports day ,the timekeeping group for running events consists of 1 chef judges,1 referee and 10 timekeepers.The chef judges and the referee are chosen from 5 teachers while the 10 timekeepers are selected from 16 students
(a)How many different timekeeping groups can be formed?

(b)If it is possible to have a timekeeping group with all the timekeepers being boys,what are the possible numbers of boys among the 16 students?

(c)If the probability of having a timekeeping gropu with all timekeepers being boys is 3/364,,find the member of boys among the 16 students

3 students are radomly selected from 10 students of different weights.Find the probabilities

(a)the heaviest student is in the radom

(b)the heaviest one out of the 3 selected students is the 4th heaviest among the 10 students

(c)the two heaviest students are not both selected