Given the data below for a 200 g salmon that is 20 cm long: (Group B) [Na^+ ECF] =212 mM [Na^+ water] = 450 mM delta X_gill = 6.4 mu _m delta X_skin = 30 mu _m A_gill = 2.0 cm^2 gm^-1 A_skin = 8 cm^2 gm^-1 D_kgill = 1.6 times 10^4 cm^2 s^-1 D_kskin = 0.2 times 10^4 cm^2 s^-1 Determine the Na^+ diffusion rate through the skin and the gills. Explain the differences in diffusion rate between the two structures. Calculate the total rate of Na^+diffusion. Assuming the fish is in sodium balance, explain the mechanisms responsible.