How can I write a opengl code for the following assignment?

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OpenGL

I want to write opengl code using C or C++ to pump water from the underground storage tank to an overhead tank when the user switches ON the motor.
Once the water in overhead tank reaches a maximum level, water has to overflow. As the motor is switched off the water should not be pumped into tank and continue to overflow untill the water level reduces to the maximum level.

I am a beginner in opengl and would be happy if someone could let me know how i can start with the problem.