A mixture of \( CO \) and \( CO _{2} \) is found to have a density \( 1.5 g / \) litre at \( 30^{\circ} C \) and \( 730 mm \). The composition of the mixture is-
1. \( CO : 44 \% ; CO _{2}=56 \% \)
2. \( CO : 32 \% ; CO _{2}=68 \% \)
3. \( CO : 70 \% ; CO _{2}=30 \% \)
4. \( CO : 9 \% ; CO _{2}=91 \% \)