How many characters does the longest word on this list contain?The largest word that's possible to assemble from the specified combination is 'hislopite', which contains 9 letters.
How many actual words can you make using this combination of letters?From this list of words that start with 'h' and include 'isl', you have 2 combinations which can be selected.
What is the highest scoring word you can play in Scrabble ?Since there are only a small amount of words to choose from, you're obligated to go with 'haisla' which scores 9 points.