Hi this question is from a grade 11, math class, in the unit Applications. please answer the question to its fullest, and show every step. thank you alot.

In 2001, Windsor, Ontario received its maximum amount of sunlight, 15.28 hrs, on June 21, and its least amount of sunlight, 9.08 hrs, on
December 21.
a) Due to the earth's revolution about the sun, the hours of daylight function is periodic. Determine an equation that can model the hours of daylight function for Windsor, Ontario.
b) On what day(s) can Windsor expect 13.5 hours of sunlight?

Question

Hi this question is from a grade 11, math class, in the unit Applications. please answer the question to its fullest, and show every step. thank you alot. 

In 2001, Windsor, Ontario received its maximum amount of sunlight, 15.28 hrs, on June 21, and its least amount of sunlight, 9.08 hrs, on 
December 21.
a) Due to the earth's revolution about the sun, the hours of daylight function is periodic. Determine an equation that can model the hours of daylight function for Windsor, Ontario.
b) On what day(s) can Windsor expect 13.5 hours of sunlight?