Task: Question Answering
Input (English): Problem: one week , a certain truck rental lot had a total of 18 trucks , all of which were on the lot monday morning . if 50 % of the trucks that were rented out during the week were returned to the lot on or before saturday morning of that week , and if there were at least 12 trucks on the lot that saturday morning , what is the greatest number of different trucks that could have been rented out during the week ? 
Options: a ) 18 , b ) 16 , c ) 12 , d ) 8 , e ) 4
Output (English): c