John is working on an infrastructure project for a city. His plan has a straight road represented by the equation, y=2x+5 , where y is the distance in meters, and x is the position along the road. The city has decided to add a new pedestrian walkway perpendicular to the road. The walkway will pass through the point (4,6). Determine the equation of the perpendicular walkway.

A. y=- 1/2 x+8
B. y=- 1/2 x-2
C. y=2x+8
D. y=2x-2