Task: Question Answering
Input (English): Problem: in assembling a bluetooth device , a factory uses one of two kinds of modules . one module costs $ 10 and the other one , that is cheaper , costs $ 6 . the factory holds a $ 80 worth stock of 12 modules . how many of the modules in the stock are of the cheaper kind ? 
Options: a ) 20 , b ) 25 , c ) 10 , d ) 30 , e ) 35
Output (English): c