2. (20 points) Write out the 3-nearest neighbor classifier for a feature x ER based on the following training points: (1) = 6,y(1) = -1, 2:(2) = 4, y(2) = -1, 1(3) = 3, 4(3) = -1, z (4) = -3, 7(4) = 1, 2 (5) = 0, y(5) = 1. Hint: the classifier shall have the following form with the threshold c to be determined. S-1, if 120