A train of 150 m/s if travelling towards north direction at a speed of 10 m/s. A bird flies at a speed of 5 m/s towards sound direction along the railway track. What will be the time taken by the bird to cross the train?

Question

$\begin{array}{1 1} (a)\; 5 s \\ (b)\; 10 s \\ (c)\; 15 s \\ (d)\; 20 s \end{array}$