The topic is chemical reaction rate.
Two substances A and B are combined to form a product C. The formation of product is proportional to the time the reactants are combined. The final product is composed of three parts of A for every part of B. If initially A is 50 lbs and B is 60 lbs, and 10 lbs of the product is formed after 45 mins., find the time it takes for the reaction to form 25 lbs.
The answer is 135 minutes. Show complete solution please. Thank you.