A hypothetical reaction ${\text{x}}_{\text{2}}{\text{+ y}}_{\text{2}}\to \text{2xy}$ follows the mechanism as given below
$\begin{array}{l}{\text{x}}_{\text{2}}\rightleftharpoons \text{x\hspace{0.17em}+ x(fast)}\\ {\text{x + y}}_{\text{2}}\to \text{xy + y(slow)}\\ \text{x + y}\to \text{xy (fast)}\end{array}$  
The order w.r.t ${\text{x}}_{\text{2}}$ is