What is the highest scoring word in Scrabble using the requested combination ?For 9 points, it's possible to use 'coof'.
How many words are there using the combination requested?From this page of words that have 'co' in and end with 'of', we have found 9 entries that are available altogether.
How many letters are in the longest word from this list?'corrosionproof', consisting of 14 letters.