$1,2-$butadiene $)=C=(CH-C{H}_3$ is isomerized to $1,3-$butadiene $)=CH-CH=(C{H}_2$ in the process below. Unreacted $1,2-$butadiene is separated from $1,3-$butadiene and recycled into the reactor. The $1,2-$butadiene contains an impurity $-$ ethyl chloride $(C{H}_{3}C{H}_{2}Cl)-$ which is difficult to remove by distillation. Ethyl chloride is purged via stream $7.$ The splitter purges $5\mathrm{.}0w{t}^{\%}\%$ of stream $5.$

a$.$ Which stream has the highest flow rate of $1,2-$butadiene?

b$.$ Calculate the flow rate of product stream $4,$ in $k\frac{g}{m}in.$

c$.$ Calculate the composition of purge stream $7.$

d$.$ Calculate the flow rate and composition of stream $2.$