Nitration of aniline by ${\mathrm{HNO}}_3+{\mathrm{H}}_2{\mathrm{SO}}_4$ mixture gives 51% para nitro derivative while 47% is meta nitro derivative and rest 2% ortho nitro derivative at 15° C. In order to obtain 276 gm of p-nitro aniline what minimum mass of aniline should be taken?