Air flows past an aeroplane wing at $70\ \text{m/s}$ over its upper surface and $60\ \text{m/s}$ under its lower surface, as shown in the figure. The wing has an area of $20\ \text{m}^2$, and the density of air is $1.2\ \text{kg/m}^3$. Using Bernoulli's principle, the upward lift on the wing is closest to

Fig. 1: Cross-section of an aeroplane wing of area 20 square metres. Air streams over the top at 70 m/s and under the bottom at 60 m/s.