a+b+c+d=4n; where a,b,c lie between 0 and n and d lies between 0 and 2n.

a+b+c+d=4n; where a,b,c lie between 0 and n and d lies between 0 and 2n.

In the examination the max marks for each of three papers is n and the
fourth paper is 2n. find the number of ways in which a candidate can gets
3n marks ?