Daylight Hours The number of hours of daylight in Anchorage, Alaska, can be approximated by the...

Daylight Hours The number of hours of daylight in Anchorage, Alaska, can be approximated by the function

d(x) = -7.1 cos(0.0172x) + 12.27

where x is the number of days since January 1.

(a) For what value(s) of x will Anchorage have 18 hours of daylight?

(b) For what value(s) of x will the number of hours of daylight in Miami reach a maximum?