Math Help - Criminal Stats

Help with a couple problems.

Police departments are increasingly becoming more diverse. In a randomly selected police department, there were 100 officers in 1980 and 120 officers in 1995. The proportion of female officers in the police department increased from 9% in 1980 to 17% in 1995. Using an alpha of .01, determine whether this is a significant difference.

a. Write a paragraph summarizing the results
b. What criticisms would you make about the analysis, measure, or results.

How do I find a p-value? How do I find the sample size. Do I just average the populations of the individuals with the 15 years in between?