According to the U.S. Statistical Abstract, the proportion of new single-family houses completed in 2003 that had exactly three bedrooms was 0.51. For samples of 30 new single-family houses completed in 2003, the distribution of sample proportion with exactly three bedrooms has mean 0.51, standard deviation 0.09, and a shape that is approximately normal. Find the sample proportion and the z-score for each of these sample counts, and characterize each as having unusually few three-bedroom houses, unusually many three-bedroom houses, or a proportion of three-bedroom houses that is not unusual:
a. 12 of 30 houses have three bedrooms
b. 16 of 30 houses have three bedrooms
c. 27 of 30 houses have three bedrooms