Rewrite each of the following statements in the form “p if and only is q.”

(i) p : If you watch television, then your mind is free, and if your mind is free, then you watch television.

(ii) q : If a quadrilateral is equiangular, then it is a rectangle, and if a quadrilateral is a rectangle, then it is equiangular.

(iii) r : For you to get an A grade, it is necessary and sufficient that you do all the homework you regularly.

(iv) s : If a tumbler is half empty, then it is half full, and if a tumbler is half full, then it is half empty.