PQR is a triangular park with PQ = PR = 200 m. A T.V.

PQR is a triangular park with $P Q=P R=200 \mathrm{~m}$. A T.V. tower stands at the mid-point of $Q R$. If the angles of elevation of the top of the tower at $P, Q$ and $R$ are respectively $45^{\circ}$, $30^{\circ}$ and $30^{\circ}$, then the height of the tower (in m) is-