shall,if necessary,enter into a separate agreement on the total number of parts to be supplied under one or more individual contracts over a specified period, and in such case,each . ..... shall have an to respectively place orders for or supply certain quantities of the parts pursuant to the provisions of such agreement. if no such agreement is entered into,notwithstanding the contents of the "plan for the total number of orders to be placed" to be separately provided by .... ... shall not have any obligation to place orders for parts,nor shall it be liable for failing ti reach the planned quantity of orders