The optimal solution of this linear programming problem is at the intersection of constraints $1$ and $2.$

Max $2$x$1+$ x$2$

s$.$t$.4$x$1+1$x$2<=400$

$4$x$1+3$x$2<=600$

$1$x$1+2$x$2<=300$

x$1,$ x$2>=0$ Over what range can the coefficient of

vary before the current solution is no longer optimal?