Sohar Aluminum buys a certain raw material from a supplier. The company's policy is to accept the shipmen if the proportion of defective parts in the shipment is less than or equal to 5%. A new shipment has arrived. A sample of 100 units was inspected and 7 parts were found to be defective. What is the critical value to test the appropriate hypotheses (at a=5%)? O a. z= 1.96 O b. z= 1.645 O c. z= 0.92 Od. z=-1.645