Studies by the Federal Highway Administration suggest that speed limits on many thoroughfares are set arbitrarily, and are often artificially low. According to traffic engineers, the ideal speed limit should be the 85th percentile speed. This means the speed at or below which 85 percent of the traffic moves. Assuming speeds are normally distributed, find the 85th percentile speed for roads with the following conditions.

The mean speed is 52 mph with a standard deviation of 8 mph.