500
" Cassio's a proper man. Let me see now: To get his place and to plume up my will. How? how?- Lets see, after some time, to abuse Othello's ear that he is too familiar with his wife." (Act 1 Scene 3 pg 72 lines 392-396)
Iago is speaking to himself about his plan to get Cassio's job by making Othello believe that he is having an affair with his wife.