As part of research on the length of the growing season in mountain, meteorological stations are installed at di erent altitudes. The temperature average rature (in degrees celcius) as well as the altitude (in meters) of each season are recorded, the resulting data being presented below: Altitude 1040 1230 1500 1600 1740 1950 2200 2530 2800 3100 Temperature 7.4 6 4.5 3.8 2.9 1.9 1.0 - 1.2 - 1.5 - 4.5 We denote by X the Altitude variable, and by Y the Temperature variable. From the altitude of a place, we try to assess its average temperature without having to set up a new station, and we opt for a linear regression model Y = a + bX. Calculate the empirical correlation coefficient between X and Y