AMC 10B 2017 Problem 10

Past Contests AMC 10 AMC 10B - 2017
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1

The lines with equations a x-2 y=c and 2 x+b y=-c are perpendicular and intersect at (1,-5). What is c ?

Answer Choices
A. -13
B. -8
C. 2
D. 8
E. 13