Compute price elasticity and explain step by step
Suppose the demand function is Q=100-P, where Q is the quantity demand and P is the price. Please calculate the price elasticity at P=10 (by comparing it with a pair of price and quantity at P=20). Calculate the change in total revenue which is P times Q moving from P=10 to P=20. Repeat the same exercise for P=70 versus P=80.
please provide step by step.