(a) The defense of sovereign immunity is waived as to any action ex contractu for the breach of any written contract existing on April 12, 1982, or thereafter entered into by the state, departments and agencies of the state, and state authorities.

(b) Venue with respect to any such action shall be proper in the Superior Court of Fulton County, Georgia. The provisions of this subsection shall be cumulative and supplemental to any other venue provisions permitted on April 12, 1982, or thereafter permitted by law.