Two designs are under consideration for manufacturing. Design I has two circuits A and B in series with the warrantee period reliability 0.8,0.7 respectively. Design II has also two circuits C and D, but in parallel with probability of failure 0.3,0.4 respectively. Costs of repairing circuits A, B, C, D are $12,$10,$40, and $30 respectively. Under the policy of replacing all defective circuits of a product during the warrantee period, which design is preferable for minimizing the total repair cost? (Any ethics questi4ons here?) If Design I is used and 100 units of the product are sold; on the average, how many units can be repaired by replacing only the circuit B