In aniline -$NH_2$ group is attached with benzene ring. - $NH_2$ group shows $+M$-effect. So, it activates the benzene ring. Hence, rate of
electrophilic substitution is increased due to increase in the electron density at o/p-position. In case of nitrobenzene, ($- NO_2$) -M-effect group deactivates the benzene ring, so in nitrobenzene rate of electrophilic substitution is lower than benzene. Hence, order of $SE$ reaction is