If $a>0$ and $b>0,$ then the eccentricity of the hyperbola
$$\frac{(x-h)^{2}}{a^{2}}-\frac{(y-k)^{2}}{b^{2}}=1 \quad \text { or } \quad \frac{(y-k)^{2}}{a^{2}}-\frac{(x-h)^{2}}{b^{2}}=1$$
is the number $\frac{\sqrt{a^{2}+b^{2}}}{a} .$
Find the eccentricity of the hyperbola whose equation is given.
$$\frac{y^{2}}{18}-\frac{x^{2}}{25}=1$$