Are the following formulas valid, satisfiable, or unsatisfiable? -\quad P(a) \rightarrow \operatorname{ExP}(x) -\quad \operatorname{ExP}(x) \rightarrow P(a) \text { - } \operatorname{ExP}(x) V \operatorname{ExIP}(x) \rightarrow A x P(x)