Why is there no mixed strategy for player 1? Why is M is dominated by mixed strategies U D?

The normal form of the game is given below: No strategy is strictly dominated by any pure and mixed strategy. Therefore, by the iterated dominance method no strategy of player 1 and player 2 is removed. So, the set of rationalizable strategies for this game is given below: R={U,M,D}{X,Y} The normal form of the game is given below: No strategy is strictly dominated by any pure and mixed strategy. Therefore, by the iterated dominance method no strategy of player 1 and player 2 is removed. So, the set of rationalizable strategies for this game is given below: R={U,M,D}{X,Y}