Cupertino is exploring a tax on Apple and other companies based on the size of their workforce. The tax would probably be structured similar to a proposal in Mountain View, said David Brandt, Cupertino’s city manager. Cupertino has paid a firm to begin polling residents about the tax and how any revenue from it should be spent, Brandt said. Apple did not immediately return a request for comment. The company has more than 25,000 employees in the Bay Area.