[填空题]
An oval-shaped superspeedway can be q ja sv5*s,r) )gj2vz,xq6cqcdescri 30 if a:izor)8x3 gswrmm8e*kbed by the curve $x^{2}+12 y^{2}=1+10 x^{2} y^{2}$ , shown in the diagram below. A F1 racing car is moving along the track with $\frac{\mathrm{d} x}{\mathrm{~d} t}=240 \mathrm{kmh}^{-1}$ when x=0.67 $\mathrm{~km}$ .
$\text { Find the value of } \frac{\mathrm{d} y}{\mathrm{~d} t} \text {, giving your answer to the nearest } \mathrm{km}^{-1} \text {. }$≈
