At the 26-flavor ice cream shoppe ... 

III.A.1.  How many different five-scoop dishes are possible when all scoops have to be different flavors? 

> binomial(26,5);
 

65780 

III.B.1.  How many different five-scoop dishes are possible if there is no prohibition against repeating flavors? 

> binomial(5+26-1,5);
 

142506 

III.C.  How many different five-scoop dishes are possible if there can be no more than two vanilla scoops, at most one chocolate scoop, and no more than three strawberry scoops? 

> with(powseries):
 

> vanilla := powpoly(1+z+z^2,z):
 

> chocolate := powpoly(1+z,z):
 

> strawberry := powpoly(1+z+z^2+z^3, z):
 

> other := powpoly(1+z+z^2+z^3+z^4+z^5, z):
 

> genfct := evalpow(vanilla*chocolate*strawberry*other^23):
 

> tpsform(genfct,z,6);
 

series(1+26*z+350*z^2+3249*z^3+23373*z^4+138854*z^5+O(z^6),z,6) 

Answer = coefficient of z^5, i.e., 138854.