barrage energy example

a) Calculate the volume of water that is available for power generation at the extremes of spring and nap tides?
b) If during the time the turbines are running, the level of the water in the bay is 2m higher that that in the sea, what is the potential energy available from the scheme?
c) Assuming the turbines and associated machinery have an overall efficiency of 30% and the average bulk price for electricity is 2p/kWh, what annual income is available? (we can assume that the height of the tides varies evenly between neap and spring levels)
d) If investors are looking for a 15% return on capital employed, what is the maximum cost of the 17km barrage if it is to be privately financed and paid for by sales of electricity?
e) Can you estimate the ratings of the generators, transformers, cables, etc (what assumptions do you have to make?)
f) Was a 2m height difference the best choice? If no, what is, and why?