b
\(\frac{y-5}{2}+\frac{y-0}{2}+\frac{y-x+10}{1}=0\)

\(y-5+y+2 y-2 x+20=0\)

\(4 y-2 x+15=0 \quad \ldots .(i)\)

\(\frac{x-5}{4}+\frac{x-0}{4}+\frac{x-10-y}{1}=0\)

\(x-5+x+4 x-40-4 y=0\)

\(6 x-4 y-45=0 \quad . .(i)\)

\(\frac{-2 x+4 y+15=0 . .(i i)}{4 x-30=0}\)

\(x=\frac{15}{2} \& 4 y-15+15=0\)

\(y=0\)

\(i=\frac{y-x+10}{1}\)

\(i=\frac{0-7.5+10}{1}\)

\(i=2.5 A=\frac{n}{10} A\)

\(n=25\)