nor touched by a boy

There are p posts set at equal distance along an array, which are either to be touched or traversed by b boys one after the other. First boy would start from the first post at the farthest start point and would run along the array to touch the nth post from the start before leaving the march, n < p. The next boy would do the same to touch the (n + 1) th pole from the start before leaving the march, and the practice continues till all the boys have traversed and touched 1 extra post than the previous boy. If there are still 5 posts left that are neither traversed nor touched by a boy, then what is p in terms of n and b?
(A) n – b + 4
(B) n + b – 4
(C) n – b + 6
(D) n + b – 6
(E) n + b + 4


[spoiler]Made up[/spoiler]