It is possible to use a sinusoidal function to model the amount of perceived daylight in a certain location over the course of a year. For Portland, Oregon, there is a minimum of 9 hours of daylight on the 1st day of winter and a maximum of 17 hours of daylight on the 1st day of summer. Let D represent the number of hours of "daylight" in Portland, Oregon, T days after the 1st day of spring (assume that T=0 corresponds to March 20th). You may assume that 1 year has 365days.

Find a formula for such a function, being sure to explain the practical meanings of any important pieces of the formula (amplitude, midline, and period). Use your formula to determine on what days of the year (month and day, not just T's value) Portland has about 11 hours of daylight and about 15 hours of daylight. Please round to the nearest day, if not exact