2. Determine whether the following arguments are valid or invalid. If they are valid, then state the rules of inference used to prove validity. If they are invalid, outline precisely why they are invalid. You do not need quantified predicate logic expressions to complete these problems. (4 marks each)

a. On any given day, if bob is wearing his hat then that day is not having sunny and warm weather. In the summer the weather is always warm. The weather today is sunny and bob is wearing his hat. Therefore, today must not be during the summer.

b. When he is not inside a building, bob is wearing his hat and his coat. When he is inside a building, bob is thinking about teaching. bob is not thinking about teaching. Therefore, bob must be wearing his coat.