In a closed vessel initially pure ${{\text{NH}}_{\text{3}}}_{\left(\text{g}\right)}$ is present at TK. At given temperature ammonia decomposes to  produce ${{\text{N}}_{\text{2}}}_{\left(g\right)}and{H_2}_{\left(g\right)}$ accordingly to $1^{st}$ order kinetics. The reaction is 50% completed in 11.5 minutes, after infinity time where the reaction is nearly 100% completed the total pressure in the vessel found to be 2 atm.If all pressures are calculated at TK , after how many minutes from beginning the total pressure in the vessel is equal to 1.8 atm ? (ln10= 2.3 log10,log2=0.3)