How does Ibsen use dramatic irony to heighten suspense in this scene?

Mrs. Linde knows that she has always loved Krogstad, and so does the audience, but Krogstad does not know this at the beginning of the scene.
Mrs. Linde knows that she is taking Krogstad's job, and so does the audience, but Krogstad does not know that this will happen.
Krogstad has always been in love with Mrs. Linde, and the audience knows it, but Mrs. Linde does not know this at the beginning of the scene.
Krogstad is going to try to take his job back from Mrs. Linde, and the audience knows it, but Mrs. Linde does not know that this will happe