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题库 / OG2021-PS-93
A service provider charges c dollars for the first 50 hours of service used per month and 40 cents for each 30 minutes in excess of 50 hours used during the month. If x is an integer greater than 50, which of the following expressions gives this service provider's charge, in dollars, for a month in which x hours of service were used?
c + 0.40x
c + 0.80x
c + 0.40(x-50)
c + 0.80(x-50)
c + 0.40(2x-50)
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