In a scatter plot of a dataset containing exactly four points, the ordinary least-squares (OLS) linear regression line of best fit is determined to be $\\hat{y} = -1.5x + 8$. The $x$-coordinates of the four points are $1, 2, 3,$ and $4$. If the $y$-coordinates of the first three points are $y_1 = 6$, $y_2 = 5.5$, and $y_3 = 3$, what must be the $y$-coordinate of the fourth point, $y_4$?