Three, Answer the following questions (15 points each, total 30 points, detailed process required)
13. (15 points) April 16, 2011 was a Saturday. Find the years in the 21st century where February has five Sundays.
【Analysis】According to the problem, the year that meets the condition must be a leap year (February has 29 days), and February 1st must be a Sunday, so we need to find the first year in the 21st century when February 1st is a Sunday; solve accordingly.

【Solution】Solution: According to the problem, April 16, 2011, was a Saturday, from which we can deduce that February 1, 2004, was a Sunday.

Thus, we can calculate in cycles of 4×7 (28) years, the years in the 21st century that meet the condition are 2004, 2032, 2060, and 2088, a total of 4 years.