Hyperbola

Let the eccentricity of the hyperbola \(H:{{{x^2}} \over {{a^2}}} - {{{y^2}} \over {{b^2}}} = 1\) be \(\sqrt {{5 \over 2}}\) and length of its latus rectum be \(6\sqrt 2\). If \(y = 2x + c\) is a tangent to the hyperbola H, then the value of c² is equal to :