Assume that $1-$bromobutane and $1-$chlorobutane form an ideal solution. At $285K,P_{\text{c}\text{h}\text{l}\text{o}\text{r}\text{o}}^{**}=7242Pa$ and $P_{\text{b}\text{r}\text{o}\text{m}\text{o}}^{**}=2756Pa.$ When only a trace of liquid is present at $285K,y_{\text{c}\text{h}\text{l}\text{o}\text{r}\text{o}}=0\mathrm{.}785.$

Part C

Calculate $Z_{\text{c}\text{h}\text{l}\text{o}\text{r}\text{o}}$ and $Z_{\text{b}\text{r}\text{o}\text{m}\text{o}}.$

Need help. I've got this answer and $0\mathrm{.}724,0\mathrm{.}276$ as an answer They are both wrong Not sure what to do