Translate each of the following arguments into symbolic form, then assess the validity of each using a truth table or truth-assignment test (your choice; three points each):
a) “Either the wealthiest people are the happiest, or it is not the case that money can buy everything. The wealthiest people are not the happiest. Therefore, money cannot buy everything.”
b) “If there are dried-up riverbeds on Mars, then water once flowed on the Martian surface. There are dried-up riverbeds on Mars. Therefore, water once flowed on the Martian surface.”