Problem: 8 men can do a piece of work in 12 days . 4 women can do it in 48 days and 10 children can do it in 24 days . in how many days can 18 men , 4 women and 10 children together complete the piece of work ? 
Options: a ) 5 days , b ) 15 days , c ) 28 days , d ) 4 days , e ) 7 days
d