4. The Computer Balance Company Ltd is developing a new minicomputer system specially designed for use in small accounting practices. The system comes complete with standard programs to deal with the routine preparation of accounts. The production of the system for a particular practice, with the necessary amendments required, can be split into the following eight activities. (The actual details are still a commercial secret.) It is possible to reduce the total time for production below the normal total time by crashing certain activities (in units of one week) at extra costs. The relevant figures are given in the table below: In addition to the above cost figures, there is a R200 per week charge for variable overhead incurred during the production of the system. Required: Using the normal durations and costs, determine the critical path and its length. What is the total cost of the project in this case