def __placeBuyOrder(self, tick):
        ''' place buy order'''
        cash=self.__getCashToBuyStock()
        if cash == 0:
            return

        share=math.floor(cash / float(tick.close))
        order=Order(accountId=self.__strategy.accountId,
                         action=Action.BUY,
                         is_market=True,
                         symbol=self.__symbol,
                         share=share)
        if self.__strategy.placeOrder(order):
            self.__position=share
            self.__buyPrice=tick.close