func: function mintTokens(address beneficiary, uint256 tokens) internal {
          uint256 weiAmount;
          if (block.timestamp >= time0 && block.timestamp < time2) weiAmount = tokens.div(11000);
          else if (block.timestamp >= time3 && block.timestamp < time7) weiAmount = tokens.div(10000);
  
          weiRaised = weiRaised.add(weiAmount);
          token.mint(beneficiary, tokens);
          addNewHolder(beneficiary);
          TokenPurchase(msg.sender, beneficiary, weiAmount, tokens, block.timestamp);
      }