$25gm.$ of Benzoyl peroxide, $,$ was used as an initiator for a free$-$radical polymerization to react vinyl acetate, VA monomer, to form high molecular weight polyiny acetate PVA at $60C.$ The polymerization reaction started with $5kg$ of VA in a five$-$liter batch reactor. What is the VA concentration at $20$min from the start of the reaction?