Prove that no matter what node we start at in a height-h binary search tree, k successive calls to "tree-successor" take O(k+h) time?

Prove that no matter what node we start at in a height-h binary search tree, k successive calls to “tree-successor” take O(k+h) time?

Check this SO post: http://stackoverflow.com/questions/8454771/how-can-i-prove-this-operation-over-binary-search-trees