Suppose that the production of a $30,000 automobile in Canada requires $10,000 worth of steel. The Canadian nominal tariff rates for importing these goods are 25 percent for automobiles and 10 percent for steel. Given this information, the effective rate of protection for the Canadian automobile industry is approximately:
选项：

A: 15 percent
B: 32 percent
C: 48 percent
D: 67 percent