A building $A,B$ is 40 m long. It cuts the shadow that is as long as the building then what is an angle $x$ in the given figure below?

Question

$\begin{array}{1 1} (a)\;30^{\circ} \\ (b)\;45^{\circ} \\ (c)\;60^{\circ} \\(d)\;none\;of\;these \end{array} $