Wind - Rain - Screen Problem

The front windscreen of a car is vertical and is made up of two parts:

• The upper part is hinged at the top so that it can be rotated about the hinge.
• The lower part is fixed.

The length of the upper part is $25\text{ cm}$ and it covers the top $5\text{ cm}$ of the lower part.

Now, the car is moving on a level road with a constant velocity of $60\text{ km}$ per hour and the rain is falling vertically at $20\text{ km}$ per hour. What is the maximum angle through which the upper part of the main screen can be raised so that the raindrops do not enter into the car?