To determine how the number of housing starts is affected by mortgage rates an economist recorded the average mortgage rate and the number of housing starts in a large county for the past 10 years. These data are listed here.

x y

8.5 115

7.8 111

7.6 185

7.5 201

8 206

8.4 167

8.8 155

8.9 117

8.5 133

8 150

Estimate with 90% confidence the mean monthly number of housing starts when the mortgage interest rate is 7%.