For the 18 hour time period beginning at midnight, the temperature F (in degress Fahrenheit) in a particular room is given by the function F(t)=-12sin(t/3)+78, where t is measured in hours

a. To the nearest degree, what is the temperature at 9 AM

evaluate F(9)
b. During which two consecutive hours does the temperature reach a maximum?

max temp will be when sin(t/3) = -1 (why?) ... sin(what values) = -1 ?
c. To the nearest tenth, what is the average temperature for the 18 hour period?

remember this ?
d. If the air conditioning turns on when the temperature is 83 degrees or higher, at what time interval(s) is the air conditioning operating?

solve for the intervals when
Thanks a lot everyone.