Combination incorrect mgmat

[Jinglander]

Ok here is a problem from mgmat that I don't agree with the answer. Please advise

Amy and Adam are making boxes of truffles for as wedding favors. They have an unlimited supply of 5 different types of truffles. If each box holds 2 truffles of different types how many different boxes can they make.

The book says it's 5!/3!2! but this seems wrong since there is a unlimited supply. Instead I would think u have 5 choices for the first and 4 for the second hense 20

[Rahul@gurome]

Though there is an unlimited supply of truffles, their types is limited which is 5 in number.
Let the types be a, b, c, d, and e.

Each box can have 2 truffles of different types.
So what we need to do is to find out the number of ways in which we can select 2 types out of the 5 types which is 5C2 = 5!/(3!2!) = 10.

You can see that the different boxes possible are ab, ac, ad, ae, bc, bd, be, cd, ce, de and they are 10 in number.