Scoring double word scores by adding an s to exsisting word?

Question

opponent used dbl word=tree. opponent #2 adds an s making trees-does he get to count the word trees as double word also?

Answer 1

Only the first one.

Scoring

Each word formed in the play is scored this way:

Any tile played from the player's rack onto a previously vacant square that is a "double-letter" (light blue) or "triple-letter" (dark blue) premium square has its point value doubled or tripled as indicated.

Add the normal point value of all other letters (excluding blanks) in the word (whether newly played or existing).

For each newly played tile placed on a "double-word" (light red) premium square, the total is doubled (or redoubled).

For each newly placed tile placed on a "triple-word" (dark red) premium square, the total is tripled (or re-tripled).

Premium squares affect the score of each word made in the same play by constituent tiles played upon those squares. Premium squares, once played upon, are not counted again in subsequent plays.

If a player uses all seven of the tiles in the rack in a single play, a bonus of 50 points is added to the score of that play (this is called a "bingo" in Canada and the United States, and a "bonus" elsewhere). These bonus points are not affected by premium squares.

When the letters to be drawn have run out, the final play can often determine the winner. This is particularly the case in close games with more than two players. The player who goes out first gets the point values of all remaining unplayed tiles added to their score. Players with tiles remaining on their rack have their equivalent point values removed from their score.

I hope this clarifies it for you.  

playgames.simplyfun.com

Answer 2

No, only the first person

Answer 3

Premiums are scored only on the play that they a covered.

But if there is a premium square following the second  e in tree, and your opponent plays dogs, also making trees with the S, the premium is scored in BOTH words.