There are 12 IR questions and 30 minutes so you should be average 2 minutes 30 seconds for each one. Generally, the graphics and table analysis questions will be *faster* to answer. The Multi-source and Two-Part Analysis questions tend to be a bit more complex but of course, it varies by type. Since you're going to get a mix of EASY/Difficult question, it's impossible to give a more precise answer.
But you should try to aim for 2 minutes and under for the average Graphics/Table Analysis questions (though there may be some tough ones thrown in there) but generally the Multi-source and Two-Part Analysis questions will (on average) take up closer to 2 min 30 seconds and maybe even 3 minutes.