Use a graph paper for this question (Take $2 \text{cms}=1$ unit on both $x$ and $y$ axis)(i) Plot the following points: $A(0,4), B(2,3), C(1,1)$ and $D(2,0)$.(ii) Reflect points $B, C, D$ on the $y$-axis and write down their coordinates. Name the images as $B', C', D'$ respectively.(iii) Join the points A, B, C, D, D', C', B' and A in order, so as to form a closed figure. Write down the equation of the line of symmetry of the figure formed.