Calculate the non-basic variable's current reduced cost, which represents the exact amount the objective coefficient must improve before the variable becomes profitable to enter the basis. The allowable change bound is reached when this reduced cost reaches zero, meaning the coefficient can vary from negative infinity up to its current value plus the reduced cost (for maximization).

You calculate it using the variable's current reduced cost and the coefficients from the optimal inverse matrix to find the exact upper and lower bounds before its reduced cost crosses zero.

In a maximization problem, a non-basic variable enters the basis when its objective coefficient increases past its reduced cost, making its allowable upper limit the current coefficient plus the reduced cost, with no lower limit. In a minimization problem, it enters when its coefficient decreases below its reduced cost, making its allowable lower limit the current coefficient minus the reduced cost, with no upper limit.

Calculate its reduced cost and adjust the coefficient until the reduced cost reaches zero, the coefficient value at that point marks the boundary of its allowable range.

Use the non-basic variable’s reduced cost and the relevant tableau coefficients to find how far its objective coefficient can change before its reduced cost reaches zero; that zero point is the boundary of its allowable range.

For a non-basic variable, use its allowable increase/decrease from the sensitivity report: the coefficient can change within that range before its reduced cost reaches 0, at which point it can become profitable enough to enter the basis.

For a non-basic objective function coefficient, calculate the allowable range by using its current reduced cost and determining how much the coefficient can increase or decrease until its reduced cost reaches zero; that range is the point at which the variable can become profitable enough to enter the basis.