A biologist is studying the relationship between the elevation of a mountain region and the temperature. The standard deviation of the elevation measurements is $s_x = 400$ meters, and the standard deviation of the temperature measurements is $s_y = 6.0^{\circ}\text{C}$. The coefficient of determination is calculated as $R^2 = 0.49$. Given that temperature decreases as elevation increases, what is the slope $\beta_1$ of the regression line?