Finding Average Rate of Reaction

Rate of reaction is a measure of how fast a reaction occur, or how much the reactant/product change in a period of time.

Example
In a chemical reaction, 2.5g of calcium carbonate react completely with excess hydrochloric acid to produce 600cm³ of carbon dioxide gas in 1.5 minutes. Find the rate of reaction in term of
a. decreasing mass of calcium carbonate
b. increasing volume of carbon dioxide gas produced