In formulating an LP model for this network:

How many decision variables are required?

Besides non$-$negativity constraints, how many constraints are required?

The constraint for supply node $1$ is:

xA$1+$xB$1+$xC$1=670$

$9$x$1$A$+7$x$1$B$+7$x$1$C$=670$

x$1$A$+$x$1$B$+$x$1$C$<=670$

$9$x$1$Ax$7$x$1$B$+7$x$1$C$<=670$

x$1$A$+$x$1$B$+$x$1$C$=670$

The constraint for demand node B is:

$7$x$1$B$+9$x$2$B$+8$x$3$B$<=500$

xB$1+$xB$2+$xB$3=500$

x$1$B$+$x$2$B$+$x$3$B$=500$

x$1$B$+$x$2$B$+$x$3$B$<=500$

$7$x$1$B$+9$x$2$B$+8$x$3$B$=500$