function setPricingStrategy(
    uint _startTime,
    uint _endTime,
    uint _rate,
    uint _weiMaximumGoal,
    uint _weiMinimumAmount,
    uint _weiMaximumAmount
)  external onlyOwner returns (bool) {
    require(!hasEnded());
    require(_endTime >= _startTime);
    require(_weiMaximumGoal > 0);

    startTime = _startTime;
    endTime = _endTime;
    rate = _rate;
    weiMaximumGoal = _weiMaximumGoal;
    weiMinimumAmount = _weiMinimumAmount;
    weiMaximumAmount = _weiMaximumAmount;
    return true;
  }