1a) Consider a spreadsheet for expenses. Columns are "date", "description", "amount", and "approval". The approval column has null (blank) values, "yes", and "no". How would you create a total that calculates only the approved -- Yes -- expenses?

b) Same expenses spreadsheet -- now how would you calculate subtotals based on descriptions? For example, many descriptions include "United Airlines". How would you create a subtotal with all the United Airlines expenses?

c) Consider the expenses spreadsheet yet again. Note that descriptions vary quite widely.. you might see a description for "United Airlines", "UNITEDAIR", "United Flight XYZ" or all sorts of different variants. Any good ideas on how to relate those expenses and rightly calculate subtotals, without having to manually associate each line of data?