[Prizmz]

Both versions are acceptable, but the latter is better because the last comma clearly separates the final items in the series. When the final comma is omitted, there is a chance the final two items become a unit like peanutbutter and jelly or ham and eggs.

The clearest use is to include one fewer commas than items in a series.

The introductory adverbial clause should be marked with a comma before "Mary" for clarity between the two elements of the thought. The rule cites the length of the introduction as the factor to use a comma or not to create lucidity.