I am not sure if this is a straightforward question or not. Basically, I have a set of products along with their prices and quantities demanded. I also have own and cross price elasticities for each product as well as the cross price elasticity with my outside good. I want to figure out how quantity demanded will change when the prices of several products changes. For example, if my products are different types of beers and the outside option is wine, I want to know how quantity demanded of all beers and wine will change when several beers change their price. I want to assume that total quantity demanded of beer and wine remain constant (but expenditure can increase). Finally, I do not want to estimate a demand model I just want to use the elasticities that I already have access to (from an outside source).