82: Sanity Checking Estimations in Cases

Many candidates forget to sanity-check their calculations in a case. That is a bad idea. Without a sanity-check there is no way to meaningfully assess the accuracy of your answer. More important, how you perform the sanity check is the key. All sanity-checks must involve the reduction of the answer to a number that you can intuitively compare to your own experiences. Unless you do this, you can never defend your answer.