A manufacturer is ring rolling ball-bearing races (see Fig. 6.43). The inner surface has a surface roughness specification of 0.10 ± 0.06 fxm. Measurements taken from rolled rings indicate a mean roughness of 0.112 fxm with a standard deviation of 0.02 /xm. Fifty thousand rings per month are manufactured and the cost of discarding a defective ring is $5.00. It is known that by changing lubricants to a special emulsion, the mean roughness could be made essentially equal to the design specification. What additional cost per month can be justified for the lubricant?