The political pollster canter is preparing for a national election. it would like to poll at least 7,500 democrats and 7,500 republicans. each mailing to the east coast gets responses from 500 democrats and 250 republicans. each mailing to the midwest gets responses from 500 democrats and 500 republicans. and each mailing to the west coast gets responses from 250 democrats and 500 republicans. mailings to the east coast cost $40 each to produce and mail, mailings to the midwest cost $60 each, and mailings to the west coast cost $50 each. how many mailings should canter send to each area of the country to get the responses it needs at the least possible cost?