Molecular weight of $CH_3NH_2$ = 31

Molecular weight of $COCl_2$ = 98

Molecular weight of $CH_3N=C=O$ = 57

**% Atom economy = Molecular weight of desired product/ Sum of the molecular weight of desired product $\times$ 100**

**= 57/31 +98 $\times$ 100**

**= 44.18%**