Quality cost indices are often used to measure and analyze the cost of maintaining a given level of quality. One example of a quality cost index, which uses a direct labor base, is computed as:

The following quality cost data were collected for May and June:

Based upon these cost data, the quality cost index:

A. Decreased four points from May to June.

B. Was unchanged from May to June.
C. Increased 10 points from May to June.
D. Decreased 10 points from May to June.

Explanation:
The index for May was 40 [(US $4,000 + $6,000 + $12,000 + $14,000) + $90,000], and the index for June was 36 [(US $5,000 + $5,000 + $15,000 + $11.000) + $100,000].