The answer is as follows: the number of winners in the class is 3+2+3+ 18+6+ 12=44.

13 of them won the second prize.

Remaining reward 44- 13*2= 18

And the number of winners is 28- 13= 15.

So the bonus is 18- 15=3.

Plus the previous item of this classmate, you can get up to 4 awards.