The following table gives the outside temperature in degrees fahrenheit on a summer afternoon:

time (pm) temperature (°f)
12: 00 78
1: 00 82
3: 15 88
4: 30 93
6: 00 91

a. calculate the average rate of change between consecutive data points in the table.
b. determine the time interval(s) when the thermometer was rising the fastest, on average.