# The number of hours of daylight H in a certain area is approximately given by the function H(t) = 2.5 cos[ b(t – d) ] + 11.5

The number of hours of daylight H in a certain area is approximately given by the function

H(t) = 2.5 cos[ b(t – d) ] + 11.5

where H is in hours and t in days, and the function has a period of one year (365 days).

a) Find b (b > 0) and d if H is maximum on June 21st (month of February has 28 days).