<s>[INST] Select the equation that corresponds to the following statement: "Cometri was sad only when he came home and it was too rainy to go out." Here, let P be the statement 'Cometri was sad," Q be 'he came home," and R be 'it was too rainy to go out." (I) P unless Q and R. (II) P if and only if Q and R. (III) P if Q or not R.[/INST]