Gerchak's note further elaborates on an example in my paper "From EOQ Towards ZI" (Zangwill, W. I. 1987. From EOQ towards ZI. Management Sci. 33 1209--1223.). My example is correct. His example is correct also, and I was aware of examples of his type when I wrote the paper as were the referees...

The non-linear programming problem seeks to maximize a function f(x) where the n component vector x must satisfy certain constraints g_i(x) - 0, i - 1, ..., m¹ and g_i(z) \geqq 0, i - m¹ + 1, ..., m. The algorithm presented in this paper solves the non-linear programming problem by transforming it...

Zero inventory (ZI) and the related concepts of Just in Time and Kanban are innovative and powerful means to improve production efficiency. This paper applies these concepts to a series facility production system and, in particular, identifies which facilities will never hold inventory...

A conceptualization of production learning is proposed, which resolves costs into groups characterized by the rate at which the costs can be reduced. These groups may correspond to learning in process, materials or technology. This approach suggests a new budget methodology, the Learning Rate...

The Chebyshev problem is to determine a point x^\alpha which solves max_\alpha min i - 1,..., N{g_i(x)}. By exploiting generalized inverses an algorithm is developed for determining x^\alpha. It is also shown that in a certain sense the Chebyshev problem is equivalent to the concave programming...