public boolean pickAndExecuteAnAction() {

		try{
		for(int i =0; i < Bills.size(); i++){
			//print("" + Customers.get(i).s );
			if(Bills.get(i).s == OrderState.needToCompute){
				Compute(Bills.get(i));
				return true;
			}
		}
		
		
		for(int i =0; i < Bills.size(); i++){
			
			if(Bills.get(i).s == OrderState.needChange){
				makeChange(Bills.get(i), i);
				return true;
			}
		}
		
		
		for(int i =0; i < MarketBills.size(); i++){
			if(MarketBills.get(i).s == mBillState.OutStanding){
				payMarket(MarketBills.get(i));
				return true;
			}
		}
		return false;}
		
		catch (ConcurrentModificationException e) {
		
			return false;
		}
				
	}