Task: Question Answering
Input (English): Problem: in assembling a bluetooth device , a factory uses one of two kinds of modules . one module costs $ 15 and the other one , that is cheaper , costs $ 10 . the factory holds a $ 140 worth stock of 13 modules . how many of the modules in the stock are of the cheaper kind ? 
Options: a ) 20 , b ) 25 , c ) 30 , d ) 11 , e ) 35
Output (English): d