7. (3pts) Find a logical proposition that is equivalent to (rq)(pq) but that only uses the connectives ,, and maybe parenthesis. Prove your answer is correct. 8. (9pts) Determine if the following are tautologies, contradictions or contingencies using truth tables. For your truth tables not to become too wide use additional variables for compound propositions. Refer to the example below. (a) (yx)((yx)(yx)) Fill in the truth table: and use it to explain if the expression is a tautology, contradiction or contingency. (b) (pq)(pr)(qr) (c) (xy)(yx)