If I am combing two atoms that always combine into a molecule of 4 atoms, how do I calculate the likely distribution of products based on the relative amounts of the two ingredients. For example: If I have equal amounts of A and B and the four possible combinations of products are A4 A3B1 A2B2 A1B3 and B4. Then if I change the amounts of A and B such as 75% A with 25% B or any other starting ratio, how do I set up to caluculate?