Reddit mentions of Introduction to Econometrics: custom edition for the University of Californica, San Diego

Well, it sounds like an econometrics problem. You have to variables price and quantity sold. There should be, at the very least, a weak relationship between the two. You can set up a regression problem to understand what the quantity sold would be considering the price. The beta1 coef. would be your elasticity. Now this will tell you the first half of your question. You could use, quantile autoregressive distributed lag models or even Box-Cox extended autoregressive models. That being said, from the comments you dont know what any of these things are. So, go read an introduction to statistics book (or in this specific use case, econometrics. Learn about regression, autoregression, instrumental variables, etc. Then try to tackle a problem. You cannot run before you can walk and you wont be able to interpret or tune your output. This was my into text: https://www.amazon.com/Introduction-Econometrics-custom-University-Californica/dp/1418080497