A → B The molecule A changes into its isomeric form B by following a first order kinetics at a temperature of 1000 K. If the energy barrier with respect to reactant energy for such isomeric transformation is 191.48 kJ mol^–1 and the frequency factor is 10²⁰, the time required for 50%, molecules of A to become B is ______ picoseconds (nearest integer). [R = 8.314 J K^–1 mol^–1]