'(b) If the Secretary makes a grant or enters into a contract under this section for a study and planning project respecting an emergency medical services system for a particular geographical area, the Secretary may not make any other grant or enter into any other contract under this section for such project, and he may not make a grant or enter into a contract under this section for any other study and planning project respecting an emergency medical services system for the same area or for an area which includes (in whole or substantial part) such area