Task: Question Answering
Input (English): Problem: a and b can finish a work in 10 days while b and c can do it in 18 days . a started the work , worked for 5 days , then b worked for 10 days and the remaining work was finished by c in 15 days . in how many days could c alone have finished the whole work ? 
Options: a ) 30 days , b ) 15 days , c ) 45 days , d ) 24 days , e ) none of these
Output (English): c