Gaseous cyclobutene isomerizes to butadiene in a first order process which has a 'k' value of 3.3×10−4 s−1 at 153∘C . The time in minutes it takes for the isomerization to proceed 40 % to completion at this temperature is _____ . (Rounded off to the nearest integer) [JEE MAINS - ONLINE - 2021]