6. The length of the day in Boulder (Latitude 40 N) can be modeled approximately by 1 1 = -3cos (365 (1 + 10)) + 12 where I is given in hours and t is the day of the year. (a) Evaluate / 81 ; fully interpret the result in the context of this problem, including units. (b) Evaluate /' 355 ; fully interpret the result in the context of this problem, including units. (c) Calculate when ( t) is largest. Explain