Let us consider the following expert system for diagnosing a cold. The database consists of the following facts: $($patient$$s fever is $37\mathrm{.}4,$ is coughing since less than $24$ hours, is sneezing, is having headache with a CF $=0\mathrm{.}4$ and is having nasal congestion with CF $=0\mathrm{.}5).$