The Overhead Rate Setter

Help me set a sensible overhead application rate for costing.

The overhead pool: [WHAT'S IN IT, TOTAL AMOUNT]
Possible allocation bases: [LABOUR HOURS / MACHINE HOURS / DIRECT COST /
OTHER]
Products/jobs and their consumption: [DESCRIBE]

Provide:
1. The allocation base that best reflects what actually drives the
   overhead
2. The overhead rate under each candidate base
3. How the choice of base changes each product's apparent cost and margin
4. Whether a single plant-wide rate is distorting things vs departmental
   rates
5. A recommendation, and when it's worth the effort of a more refined
   approach

Show how the allocation choice can make a product look profitable or not,
and pick the least distorting method.