If x² − y² + 2 hxy + 2gx + 2 fy + c = 0 is the locus of a point, which moves such that it is always equidistant from the lines x + 2y + 7 = 0 and 2x − y + 8 = 0 , then the value of g + c + h − f equals
a. 14
b. 6
c. 8
d. 29