2NO(g) + Cl₂(g) $\rightleftharpoons$ 2NOCl(s)

This reaction was studied at $-$10$^\circ$ and the following data was obtained

Run	${[NO]_0}$	${[C{l_2}]_0}$	${r_0}$
1	0.10	0.10	0.18
2	0.10	0.20	0.35
3	0.20	0.20	1.40

${[NO]_0}$ and ${[C{l_2}]_0}$ are the initial concentrations and r₀ is the initial reaction rate.

The overall order of the reaction is __________. (Round off to the Nearest Integer).