The decomposition of hydrogen is a first order reaction with a rate constant of 2.7 x 10^5s^-1 at 25 C. Assuming the initial concentration of H2O2 is 0.75 M. Determine (a) the concentration of H2O2 after 1.5 h, and (b) the time (in h) or the concenration to drop to 0.25 M.