A builders' merchant sells sand in bag A and in bag B. Bag B contains $25\%$ more sand than bag A, and bag B's price per kilogram is $10\%$ less than bag A's price per kilogram. If the price of bag B were increased by £1.35, the two bags would have exactly the same price per kilogram. What is the price of bag A?

• A£13.50
• B£10.80
• C£5.40
• D£12.15

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