A company can produce three products A, B and C. The products yield a contribution of Kshs. 8, 5, and 10 respectively. The products use a machine which has 400 hours capacity in the next period. Each unit of the products uses 2, 3 and 1 hour respectively of the machine's capacity. There are only 150 units available in the period of a special component which is used singly in products A and C. 200 kg only of special alloy is available in the period. Product A uses 2kg per unit and product C uses 4 kg per unit. There is an agreement with a trade association to produce no more than 50 units of product B in the period. The company wishes to find out the production plan which maximises contribution. 4 Find the critical path and calculate the slack time for the following network.