Inactive Tutor answered 12/08/19
If each boy is eligible for all the prizes, the 1st prize can be given away to any one of the boys and thus it can be given away in 3 different ways.
Similarly, the 2nd prize can be given away to any one of them in 3 different ways again and so on.
Hence, the total number of way all 4 prizes can be given away is 3*3*3*3 = 34 = 81