    function updateBaseRate(uint newBaseRatePerYear) public {
        // check the current block number
        uint blockNumber = block.number;
        uint deltaBlocks = blockNumber.sub(lastUpdateBlock);


        if (deltaBlocks > updateFrequency) {
            // pass in a base rate per year
            baseRatePerYear = newBaseRatePerYear;
            lastUpdateBlock = blockNumber;
            emit NewInterestParams(baseRatePerYear);
        }
    }
