Two-Stage and Big M

When the profit row contains no negative values...

• Profit cannot be increased further

• No feasible solution exists

• The problem is unbounded

If the theta values are all negative or zero...

• The problem is unbounded

• You have reached the optimal solution

• You must have made a mistake - this is impossible

• No feasible solution exists

In the Big-M method, when do we first have a feasible solution?

• Once all artificial variables are non-basic

• Profit is no longer negative

• At the very end

• When all theta values are positive

In the two-stage method, when do we first have a feasible solution?

• Once all artificial variables are non-basic

• The value in the I row is zero

• At the very end

• When all theta values are positive

How can you tell that no feasible solution exists?

• The only negative number in the bottom row is value

• Profit is negative value

• Theta values are all zero or negative

• You performed an iteration in which nothing changed

What does it mean if your profit value is negative?

• You have reached the optimal solution

• You have reached a feasible solution

• Your solution is not optimal

• Your solution is not feasible

In the two-stage method, what do you do once a feasible solution has been reached

• Stop, job done!

• Delete the artificial columns and I row

• Carry on like usual

• Restart - you must have made a mistake

In the Big M method, what do you do once a feasible solution has been reached

• Stop, job done!

• Delete the artificial columns and I row

• Carry on like usual

• Restart - you must have made a mistake