If the angles of elevation of the top of a tower from two points at a distance of $4\;m$ and $9\;cm$ from the base of the tower and in the same straight line with it are complementary. The height of the tower is ______

Question

$\begin{array}{1 1}(A) \; 36 \;m \\(B)\; 6\;m \\(C)\;18\;m \\(D)\;\sqrt {18}\;m \end{array}$