Would like to see the following problem worked out. Having trouble solving. Explanation would be helpful.

Given:Water at 20 Degrees C is filled to the top of a 15 m high, 15 m diameter tank. The tank is connected to a 15 m section of 5 cm diameter pipe which contains a fully open globe valve.
a) Determine the initial volumetric flow rate from the tank when the value is opened.
b) If the flow rate from the tank was constant in time, determine the amount of time required to empty the tank.
c) Apply and simplify the appropriate equations that could be solved to calculate the volumetric flow rate from the tank as a function of time.
d) Solve the equation in part c. to calculate the flow rate as a function of time.