Instructions: In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Input: Problem: what is the measure of the radius of the circle inscribed in a triangle whose sides measure 4 , 11 and 12 units ? 
Options: ['a ) 1.6 units', 'b ) 6 units', 'c ) 3 units', 'd ) 5 units', 'e ) 12 units']
Output:
a