func: function depositFunds(uint _amount, bytes _merkleTreeHash)
          public
          onlyIfWhitelisted("depositFunds", msg.sender){
          require(appc.allowance(msg.sender, address(this)) >= _amount);
          registerBalanceProof(_merkleTreeHash);
          appc.transferFrom(msg.sender, address(this), _amount);
          balance = balance + _amount;
          emit Deposit(_amount);
      }