Data on Cost, Demand, and Supply for a Balanced (Total $\mathrm{X}_{i j}$

Multiple Choice

Data on cost, demand, and supply for a balanced (total supply equals total demand) transportation problem is given in the table below. In the linear programming formulation of this transportation problem with $\mathrm{X}_{i j}$ denoting the amount shipped from supply point $i$ (1 or 2 ) to demand point $j(1,2$ , or 3 ) , the correct constraint to make sure that supply available in supply point \# 2 will be fully used is

A) $7 X_{21}+2 X_{22}+5 X_{23}=300$
B) $X_{21}+X_{22}+X_{23}=300$
C) $7 X_{21}+2 X_{22}+5 X_{23} \geq 300$
D) $X_{21}+X_{22}+X_{23} \geq 300$