The force required for a total combined deflection of 45 mm through the two springs is

Question

A Helical spring of 10 N/mm rating is mounted on top of another helical spring of 8 N/mm rating. The force required for a total combined deflection of 45 mm through the two springs is       

         (a) 100 N                             (b) 150 N

         (c) 200 N                             (d) 250 N