An auditor desired to test credit approval on 10,000 sales invoices processed during the year. The auditor designed a statistical sample that would provide a 6% risk of assessing control risk too low that not more than 13% of the sales invoices lacked approval. The auditor estimated from previous experience that about 6.5% of the sales invoices lacked approval. A sample of 200 invoices was examined and eleven of them were lacking approval. The auditor then determined the achieved upper precision limit to 11%,In this sample

a. Answer not given

b. The auditor will not decide to increase or decrease the level of planned control risk

c. The auditor will decide to increase the level of planned control risk

d. The auditor will decide to decrease the level of control risk.