In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Q: Problem: the radius of a sphere is increased by 10 % . the surface area increases by ? 
Options: ['a ) 21 %', 'b ) 31 %', 'c ) 41 %', 'd ) 51 %', 'e ) none of these']

A: a
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Q: Problem: what is the radius of the incircle of the triangle whose sides measure 5 , 12 and 13 units ? 
Options: ['a ) 2 units', 'b ) 12 units', 'c ) 6.5 units', 'd ) 6 units', 'e ) 7.5 units']

A: a
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Q: Problem: the length of a rectangle is reduced by 22 % . by what % would the width have to be increased to maintainthe original area ? 
Options: a ) 15 % , b ) 20 % , c ) 28 % , d ) 35 % , e ) 40 %

A:
c
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