In 2012, Canadian Tire Corporation reported sales revenue of $11,427.2 million, cost of goods sold of $7,929.3 million, and profit of $499.2 million. In 2011, it reported sales revenue of $10,387.1 million, cost of goods sold of $7,326.4 million, and profit of $467.0 million.

(a) Calculate the gross profit margin and profit margin for each year.

(b) Comment on Canadian Tire's changing profitability.