Machines A and B always operate independently and at their respective constant rates. When working alone, Machine A can fill a production lot in 5 hours, and Machine B can fill the same lot in x hours. When the two machines operate simultaneously to fill the production lot, it takes them 2 hours to complete the job. What is the value of x ?
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A$$3 \frac{1}{3}$$
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B3
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C$$2 \frac{1}{2}$$
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D$$2 \frac{1}{3}$$
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E$$1 \frac{1}{2}$$