A Manufacturer of an Anti-Inflammatory Drug Claims That the Drug $\%$

A manufacturer of an anti-inflammatory drug claims that the drug will be effective for 6 hours. An independent testing service determined that the drug was effective for only 85 $\%$ of the length of time claimed by the manufacturer. Find the length of time the drug will be effective as determined by the testing service.

A) 5.5 hours
B) 5.1 hours
C) 5.7 hours
D) 4.5 hours
E) 4.7 hours