How many 2x12 will it take to resupport the ceiling plate of a 17-foot load bearing wall to be removed from between 2 12-foot rooms and how many vertical 2x4 more than three are needed on the ends?

Consult the services of a local structural engineer with experience in wood frame construction. It would be irresponsible to answer this question without detailed knowledge of the work proposed, local building codes or by anyone other than an engineer.