We study the problem of optimally controlling a multiserver queueing system. Customers arrive in a Poisson fashion and join a single queue, served by N servers, S <Subscript>1</Subscript>,S <Subscript>2</Subscript>,… , S <Subscript>N</Subscript>. The servers have different rates. The service times at each server are independent and exponentially distributed....</subscript></subscript></subscript>