Answer:
'The mercenaries fought for as long as they were paid, not just the 40 days a year that knights fought.'
Explanation:
This supports the statement that hired soldiers would fight for longer than knights would. They had motivation which was currency in exchange for their participation in battle/war. The knights on the other hand were only required a certain amount of days. It was not stated whether they were paid or not, but I can assume that they were not which would make one--specifically--a knight reluctant to go to battle. Therefore, hired soldiers did the work the knights were reluctant to do.
Short paragraphs, un varied punctuation, the redundant use of the subjects name