You have a cylindrical tank with an open top. You are free to take the radius and height of the tank so long as both are

[answerhappygod]

You have a cylindrical tank with an open top. You are free to take the radius and height of the tank so long as both are within 2 to 5 meters. At the bottom there is a tap that can be opened and closed.
The tank is initially empty and is filled (and emptied again) through the following process.
 Phase I: The tank is filled to 86.5% of its total capacity with the help of a hose for which the flow rate has the form:
−𝑡 𝑚3 𝑄 = 𝑄𝑜𝑒 𝜏0, [ 𝑠 ]
 Where 𝑄0 and 𝜏0 are parameters that you are free to choose (so long as they are not absurd). 
 Phase II: Once the tank has been filled to 86.5% of its total capacity, the tap at the bottom of the
container is opened and the water starts flowing out of the tank. However to keep the level of water at a constant level, water from the hose is turned on again as well. This phase continues until the amount of water drained through the tap is equal to the amount stored in phase I (i.e. 86.5% of total capacity)
 Phase III: Once phase II is completed, the hose is switched off, until all the water is drained from the tank through the tap.
You are to explore the behavior of the flow rate into and out of the tank and the mass of the fluid in the tank as a function of time as well as any other variables (such as the depth of fluid in the tank) that you see fit.