using the following function identify the optimal sales strategy

max$={\displaystyle \underset{j=1}{\overset{n}{}}}{P}_j{x}_j=P_1{x}_1+P_2(x_2+x_4)+P_3{x}_3$

$\backslash$table$[[$Option$,$Grad$(\%),$Iron Price $$,$Production$($ton$),$Direct Sales,Blended Sale$],[$P$1,31,90,20,000,$x$1,],[$P$2,30,80,,,$x$2+$x$4],[$P$3,28,72,30,000,$x$3,]]$