The angles of elevation of the top of a tower from two points `P` and `Q` at distances `m^2` and `n^2` respectively, from the base and in the same straight line with it are complementary. The height of the tower is `(m n)^(1//2)` (b) `m n^(1//2)` (c) `m^(1//2)n` (d) `m n`