There are 300 combinations for EX3 alone!
There are 25 different flavours that could go in the "top slot" in Ex3, For each of these there are 24 other flavours that could go in the 2nd slot in Ex3. This would give 25*24 = 600 combinations. However, we need to divide this by 2, to get 300, as each pair of flavours would occur twice in Ex3. For example, one combination would have Chicken in the top-slot and Beef in the 2nd-slot; while another combination would have Beef in the top-slot and Chicken in the 2nd-slot.
Where does your 252 come from?
Alan