A review of the Advanced level on a small list of sales leads. Tasks mix the array functions, QUERY, SPLIT, the REGEX functions and IMPORTRANGE, the way real requests do: nobody tells you which function to use.
Before writing, decide what shape the answer has. One number goes in one cell; a list spills, so check there's room below and to the right. For a whole column of results, one ARRAYFORMULA in the top cell is tidier than a formula in every row.