homework and exercises - How to compute the speed necessary for an airplane to fly?

I give some physics lessons to a friend. She asked me a question that I am unable to answer. Could you help me ?

A plane has a weight of $2\times10^6$kg. The surface of the wing is $1200 \text{m}^2$. We assume an air density equal to $1\text{kg}/\text{m}^3$. The speed of air under the wing is $100\text{m}/\text{s}$. What should be the speed of air over the wing so that the plane remains in the air ?

I searched for expressions of lift (as for instance on Wikipedia http://en.wikipedia.org/wiki/Lift_(force)) and tried to link it with the speed of fluid over and under the wing but didn't find anything relevant with the only pieces of information I have in the exercise. In my opinion, the speed of air will depend on the shape of the wing... And if we don't know anything about the shape, we are unable to answer the question. Am I wrong ?

Any idea ?

Answer

Considering the tag "homework" I know the solution that was expected. Bernoulli law:

$$\frac{\rho v_{under}^2}{2} + p_{under} = \frac{\rho v_{over}^2}{2} + p_{over}$$

$v_{over}$ and $v_{under}$ are the air flow speeds over and under the wing respectively, $p$ is pressure, $\rho$ is the air's density. The desired lift force should be equal to the plane's weight:

$$Mg = F = S (p_{under} - p_{over})$$

$S$ is the wing's area, $M$ is the plane's mass.

You know everything (except $v_{over}$), so you can solve the system to find it.