The improvement made by changes in the system was . . . . . . . . and did not warrant the large expenses.

The other options are incorrect for the following reasons:

• Large: The improvement was not large enough to justify the large expenses.
• Small: The improvement was not small enough to be considered insignificant.
• Minute: The improvement was not so small that it could not be measured.
• Uncertain: The improvement was not uncertain; it was simply not large enough to justify the large expenses.

I hope this helps! Let me know if you have any other questions.