a 2.6 m diameter penstock carries water at a velocity oif 7 m/s to an 80% efficient hydroelectricity generation facility in west virginia that oroduces 12 mw. another 2.275 m diameter penstock carries water at a velocity of 3 m/s to a 74% efficient hydroeelctricity geenration facility in arkansas that produces 9 mw. what is the ratio of the heads of arkansas' reservoir to west virginia's reservoir?