When I was in high school, there were still moonshiners in the area. Moonshine $($illegal high$-$alcohol content ethanol$-$based whiskey$)$ is typically made as a batch distillation of fermented corn. Usually the operation was hidden in an underground or partially undergound structure

Suppose a still $($distillation unit$)$ loses the condenser and puts $3lbm$ of ethanol vapor in an enclosed space, $=1.$ If the vapor$/$air composition is in the flammable range, it will ignite when it encounters an ignition source $($the fire under the still$)$ Given such an explosion, what is the overpressure in kPa$50$ feet from the ignition source?