Which of these statements are correct? (i) The unit of $k$ for a first order reaction stays the same when the concentration is measured in bar instead of mol/L. (ii) The half-life of a zero order reaction doubles when the start concentration doubles. (iii) A first order reaction is about 94 % complete after four half-lives. (iv) For a zero order reaction a graph of $\ln[R]$ against time is a straight line.