function _update(
        uint128 baseBalance,
        uint128 fyBalance,
        uint112 _baseCached,
        uint112 _fyTokenCached
    ) private {
        ....

            cumulativeBalancesRatio +=
                (scaledFYTokenCached / _baseCached) *
                timeElapsed;
        ....
    }
  a = (b/d)*c
  0 = (5/10)*2

  a = (b * c)/ 2
  1 = (5 * 2)/10
