Given log^10 x = a, log^ 10 y = b and log^10 z = c, (i) write down 10^2a - 3 in terms of x. (ii) write down 10^3b - 1 in terms of y. (iii) if log^10 P = 2a + b/2 - 3c, express P in terms of x, y and z.