Run the loop

Column generation on the 25-foot order, one round at a time: solve, read the prices, ask the knapsack, add.

Try this. Step to the end. Three patterns get added, the number falls from 7 to 6.5, and the last round is the one that proves there is nothing left.

The last round is not wasted work. It is the round that proves the previous answer was already optimal, and without it you would only have a good number rather than the right one.