Twenty samples were taken from a cable manufacturing machine while it was being operated under closely controlled conditions. The number of defects per 100 meters for the samples is recorded below:

4, 4, 5, 3, 6, 2, 2, 4, 5, 3, 4, 2, 3, 2, 4, 5, 5, 7, 5, 3.

Determine 3 control limits (use appropriate chart) for monitoring defects of the process.