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Age 14 to 16 Challenge Level:

At a well known store they sell their own blend of coffee. They use:

Mocha costing £13 per kilogram
Kenyan costing £14 per kilogram
Brazilian costing £17 per kilogram

To make 11 kilograms of this blend of coffee costs £15 per kilogram.
This blend uses more Brazilian than Kenyan coffee.
An exact number of kilograms of each type of coffee is used.
How many kilograms of each type of coffee are used?