The National Weather Service keeps track of the temperature for a given day in a given city. It also keeps track of this information at certain times during a given day. The following temperatures were recorded on a January day in New York City.
 Time of Day
 10 AM
 12 Noon
 2 PM
 4 PM
 6 PM
 8 PM
 10 PM
 Temperature 
 30
 35
 36
 36
 34
 30
 28
 Determine the average rate of change (including units and sign) of temperature with respect to time over the entire twelve-hour period given in the table. 
 a.
 The average rate of change of temperature with respect to time over the entire 12-hour period is approximately -0.167 degrees per hour.
 b.
 The average rate of change of temperature with respect to time over the entire 12-hour period is approximately 0.167 degrees per hour.
 c.
 The average rate of change of temperature with respect to time over the entire 12-hour period is approximately -6 degrees per hour.
 d.
 The average rate of change of temperature with respect to time over the entire 12-hour period is approximately 6 degrees per hour.