The Following Represents the Financial Information of Fabriz Corporation, a Manufacturer

The following represents the financial information of Fabriz Corporation, a manufacturer of electronic components, for two months:
$$\begin{array} { l r r } & \text { March } & { \text { April } } \\\text { Sales } & \$ 539,000 & \$ 495,000 \\\text { Costs: } & & \\\text { Process inspection } & 3,300 & 3,760 \\\text { Scrap } & 3,700 & 3,860 \\\text { Quality training } & 37,600 & 26,000 \\\text { Warranty repairs } & 8,600 & 9,600 \\\text { Testing equipment } & 14,000 & 14,000 \\\text { Custorner complaints } & 5,600 & 6,800 \\\text { Rework } & 34,000 & 37,000 \\\text { Preventive maintenance } & 27,000 & 19,000 \\\text { Materials inspection } & 13,000 & 9,600 \\\text { Field testirg } & 18,800 & 24,800\end{array}$$
Required:
a. Classify these items into prevention, appraisal, internal failure, or external failure costs.
b. Calculate the ratio of the prevention, appraisal, internal failure, and external failure costs to sales for March and April.