A study was conducted to determine the amount of heat loss for a certain brand of thermal pane window. Three different windows were randomly subjected to each of three different outdoor temperatures. For each trial the indoor window temperature was controlled at 68 degree F and 50 percent relative humidity. The heat losses at the outdoor temperature of 20 degrees F were 86, 80, and 77. The heat losses at the outdoor temperature of 40 degrees F were 78, 84, and 75. The heat losses at the outdoor temperature of 60 degrees were 33, 38, and 43.  Use the simple linear regression model to find a point prediction of and a 95 percent prediction interval for the heat loss of an individual window when the outdoor temperature is:

     a) 30 degrees F

     b) 50 degrees F