Reaction mechanism – rate-determining step and order

2017 1 question

1. Mechanism of a hypothetical reaction $X_2 + Y_2 \rightarrow 2XY$ is given below: (i) $X_2 \rightarrow X + X$ (fast) (ii) $X + Y_2 \rightleftharpoons XY + Y$ (slow) (iii) $X + Y \rightarrow XY$ (fast). The overall order of the reaction will be