The surface of water in a water tank of cross section area \( 750 \,\text{cm}^2 \) on the top of a house is \( h \,\text{m} \) above the tap level. The speed of water coming out through the tap of cross section area \( 500 \,\text{mm}^2 \) is \( 30 \,\text{cm/s} \). At that instant, \( \frac{dh}{dt} \) is \( x \times 10^{-3} \,\text{m/s} \). The value of \( x \) will be _______.