A bureau de change quotes two rates, both in dollars per pound. When it sells dollars to a customer, its rate is 4% below the mid-market rate. When it buys dollars back from a customer, its rate is 4% above the mid-market rate. It makes no other charge. A traveller changes £750 into dollars and then, without spending any of them, immediately changes all of the dollars back into pounds. What percentage of her £750 has she lost? Give your answer to 1 decimal place.

• A$7.7\%$
• B$7.8\%$
• C$8.0\%$
• D$8.3\%$

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