Confidence interval on proportion difference

Question:

A survey reported in Time magazine included the question ''Do you favor a federal law requiring a 15 day waiting period to purchase a gun?" Results from a random sample of US citizens showed that318 of the 520 men who were surveyed supported this proposed law while 379 of the 460 women sampled said ''yes".

Use this information to find a 95% confidence interval for the difference in the two proportions, Pm-Pw , where Pm is the proportion of men who support the proposed law and Pw is the proportion of women who support the proposed law.