50 Kg of ammonium sulphate (NH_4 )_2 SO_4 and 30 Kg of urea CO(NH_2 )_2 fertilizers were applied in two equal sizes of plots A and B to enrich their nitrogen content. Show by working which plot was more enriched with nitrogen. (N =14; S =32; O =16 ; C =12 ; H = 1) (KCSE 2011 paper question 19.)