b
\(P_{\text {total }}= P _{ A }^{0} X _{ A }+ P _{ B }^{0} X _{ B }\)

\(=37 \times 0.5+119 \times 0.5\)

\(=78\)

\(P _{ A }= Y _{ A } P _{\text {total }}\)

\(\therefore y _{ A }=\frac{ P _{ A }}{ P _{\text {total }}}=\frac{ P _{ A }^{0} X _{ A }}{ P _{\text {total }}}=\frac{37 \times 0.5}{78}=0.237\)