public ActionResult Pay(int gasPumpIndex, int cashRegisterIndex)
{
// get selected gas pump and cash register
GasPump gasPump = Context.GetGasStation().GetGasPumps()[gasPumpIndex];
CashRegister cashRegister = Context.GetGasStation().GetCashRegisters()[cashRegisterIndex];
// call 'AcceptInput' on selected cash register
cashRegister.AcceptInput(gasPump.GetPaymentAmount());
return(RedirectToAction("Index", new { gasPumpIndex }));
}