The cost of operating an aircraft consists of landing and take-off costs of 1 thousand dollars per one landing and take-off and fuel costs of f dollars per mile flown. How much, in thousands of dollars, does it cost per week to operate an aircraft which makes one landing and take-off per day and flies m miles per week?
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A7l+1000fm
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B$$\frac{7000l+fm}{1000}$$
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Cl+fm
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D$$\frac{7l+1000fm}{1000}$$
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E7000lfm
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正确答案: B