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: if the sides of a triangle are 26 cm , 18 cm and 10 cm , what is its area ? 
Options: ['a ) 90', 'b ) 110', 'c ) 130', 'd ) 140', 'e ) 150']
Output:
a