The risk manager of your firm is attempting to determine if her recently instituted luncheon exercise program has made a difference in health care expenses. She has gathered information about the firm's medical expenses for twelve individuals who have joined her program. These information are provided in the table below:

Individual        Linda               Kim            Sarah         Matthew                Jesse            Nathan            Karen              Ruth           Tina     Gary       Fred        Jayson

BPE                    68                    44               30              58                           35                 33                   52                    69             23          69          48               26

AJE                     59                   42               20              62                             25               30                     56                    62              25          75          40              26

a. Construct a 95% confidence interval for the difference between the medical expenses before and after joining the program.

b. At the 5% level of significance, has the program reduced the monthly medical expenses? (show all work)