I tried two methods here. First, the usual one of checking different arrangements with a 3,1,1 distribution and the other with a 2,2,1 distribution and calculating their respective combinations. Works out to a total of 108. Again a long method. So wanted a shorter one.
Then i tried the "Stars & Bars" approach. I first gave each row a ball so am left with 2 balls and 6 spaces to fill. But somehow I am unable to arrive at the right answer. Could someone help point out the flaw in reasoning? Thanks.