IESDS on game with no strictly dominated strategies.

Question

I am trying to figure out a question that involves using IESDS to removed the dominated strategies from a game in order to arrive at a Nash equilibrium. However, the problem in question does not appear to have any strictly dominated strategies that I could remove for either player, resulting in an infinite loop of turns. What part of IESDS am I missing that would allow me to solve it with IESDS?

Here is the game (S chooses columns, and D chooses rows):

Answer 1

You also need to check dominance by mixed strategies. For instance, for S a mixture of the last two columns dominates the second column.