A medical researcher stores lab materials in a freezer. To make sure materials are properly frozen and safe to use for their work, the freezer must stay within 5 degrees of the ideal temperature of 18 degrees Fahrenheit. Several times a day a lab manager checks the freezer display to make sure the materials are being stored at a safe temperature. Decide if the following temperatures are safe for the researcher's work. Write Yes if the temperature is acceptable, and No if the temperature is not safe.