The first-order rate constant for the gas phase decomposition of dimethyl ether is 3.2 x 10-4s-1at 450 °C. The reaction is carried out in a constant volume container. Initially only the reactant, dimethyl ether, is present and the pressure is 0.312 atm. What is the pressure (in atm) of the reactant after 214 seconds? Assume ideal-gas behaviour.