A General Linear Demand Function Has the Form to Follow $q = k p + b$

Multiple Choice

A general linear demand function has the form to follow. $q = k p + b$ (k and b constants, with $k \neq 0$ )

Obtain a formula for the elasticity of the demand at a unit price p.

A) $E = - \frac { p } { k + b }$
B) $E = b + k p$
C) $E = - \frac { k p } { k p + b }$
D) $E = \frac { k p } { b }$
E) $E = - \frac { p } { p + b }$