In the set of real numbers $R,$ an operation $^\ast$is defined by $a^\ast b=\sqrt{a^{2}+b^{2}}.$ Then the value of $(3^\ast4)^\ast 5$ is

Question

$$\begin{array}{1 1}(1)5&(2)5\sqrt{2}\\(3)25&(4)50\end{array}$$