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|      |rate X time +(over rate X over time)  = wage |
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|Mary  |5.50 |   40 |      7.60  |  6.5       |      |
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|Mark  |4.75 |   40 |      6.85  |    5       |      |
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|Martin|6.00 |   40 |      8.10  |    8       |      |
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wage$ = rate$ X time$ + over rate$ X over time$;