12. Find the acute angle between the following pairs of lines: (a) y = 2x-3, y = x +1; (d) y + 1 = 0, x√3-y-2=0 (b) 4x + 3y = 5, 3x - 4y = 1; (e) x+2y-4 = 0, 5x+6y+7=0 (c) y = 1/2x, y = 2x; (f) x-1=0, x√3+y-2=0​