Hydropower is attractive because it produces little CO2, and provides inherent energy storage. In places without abundant natural water flow, 'pumped hydro' can serve this energy storage purpose. A particular project has a height difference between water levels of 258 m. The advertised power generation is 400 MW (when water is flowing from top to bottom). a. [2] Estimate the flowrate of water in [m3/s] required to generate the 400 MW, assuming 50% conversion efficiency [mechanical to electrical]. b. [2] What area would be required, with 10 m depth, to store one week of usage at 400 MW. c. [2] What is the effective energy density of the stored water (GJe/tonne), and how does it compare to stored coal (GJe/tonne)?