A spring of mean radius 40 mm contains 8 action coils of steel (N = 80000 N/mm2
), 4 mm in
diameter. The clearance between the coils being 1 mm when unloaded, the minimum compressive
load to remove the clearance, is
(A) 25 N
(B) 30 N
(C) 35 N
(D) 40 N