The given line segment has a midpoint at (3,1). What is the equation, in slope-intercept form, of the perpendicular bisector of the given line segment?

A. [tex][tex]\( y = \frac{1}{3} x \)[/tex][/tex]
B. [tex][tex]\( y = \frac{1}{3} x - 2 \)[/tex][/tex]
C. [tex][tex]\( y = 3 x \)[/tex][/tex]
D. [tex][tex]\( y = 13 x + 18 \)[/tex][/tex]