Let a_1, a_2, …, a_n be in A.P. If a_5=2 a_7 and a_11=18, then 12(1/(√(a_10)+√(a_11))+1/(√(a_11)+√(a_12))+…+1/(√(a_17)+√(a_18))) is equal to ____.

Let $\displaystyle a_1, a_2, \ldots, a_n$ be in A.P. If $\displaystyle a_5=2 a_7$ and $\displaystyle a_{11}=18$, then $\displaystyle 12\left(\frac{1}{\sqrt{a_{10}}+\sqrt{a_{11}}}+\frac{1}{\sqrt{a_{11}}+\sqrt{a_{12}}}+\ldots+\frac{1}{\sqrt{a_{17}}+\sqrt{a_{18}}}\right)$ is equal to $\displaystyle \_\_\_\_$.