Example: Determine the number of 10 combinations of multiset s={3·a,4·b,5·c} Solution: Let generating functions of (a be f(y), f(y)=(1+y+y2+y)(1+y+y2+y3+y4)(1+y+y2+y3+y4 +y =1+3y+6y2+10y3+14y4+17y+18y+17y+14y8+ 10y+6y0+3yll+y2▪ Example: Determine the number of 10- combinations of multiset S={3·a,4·b,5·c}. ▪ Solution: Let generating functions of {ar } be f(y)， ▪ f(y)=(1+y+y2+y3 )(1+y+y2+y3+y4 )(1+y+y2+y3+y4 +y5 ) ▪ =1+3y+6y2+10y3+14y4+17y5+18y6+17y7+14y8+ 10y9+6y10+3y11+y12