Suppose that an astronomer needs at least 13 hours of darkness to complete an observation. Using the function you found in Question 1, set up an inequality and solve it algebraically to determine between which two dates the observation can be made.
(When converting to dates, for example, day 1 is January 1st, day 32 is February 1st, etc. Also be sure to clearly identify the starting and ending dates for the observation window. Order matters here...spring to fall is not the same as fall to spring)