The calculations are really very basic. You will be provided with set up costs for your project, and a payback period. You don’t need to calculate these. You’ll also be provided with a figure for yearly profit after payback. As the project is on a 10 year timeframe, you’ll want to calculate the net profit over that time frame. So, in terms of maths, it’s a simple multiplication.
The maths is the least of your worries in the group task, obviously. To do well, what you need is basically this:
First, use the preparation time wisely. You’ll be given about 20 minutes or so (not sure about the exact time frame) to go through the material.
Obviously, you can’t get through all of it in that time frame. So, speed-read through it and make sure you find all the key information you need, basically, all the info that is relevant to your task. Lots will be either irrelevant or immaterial. Also, give a thorough reading to the option you have been given. Spot all the advantages and disadvantages, and run the basic calculations I mentioned before.
Secondly, once you start the task, first wait to hear everybody’s options and keep notes about them. Also, obviously, present your own option, and try to give all the info, but as briefly and to-the-point as you can.
Once you have all the options, quickly size them up and decide which one(s) seems the best fit, in terms of the numbers, the background info, the client’s needs etc, and try to convince the others about your opinion. Don’t be afraid to speak up, make sure you have solid arguments to back up your opinions, and also make sure you don’t present a half-baked opinion that you haven’t thought through. That’s probably an instant failure if they spot you doing that. That said, don’t be afraid to change your opinion if you get new information that changes the situation.
People will suggest trying to “chair” the discussion or being the “time-keeper” (ie annoying type that reminds people they only have x minutes left). Both can be good and will probably get you extra points, but make no mistake. The task is basically about seeing you “selling” your opinion to the others, backing it with solid arguments, but also genuinely listening to the opinions of the other people and taking them into consideration. It’s also about being able to take in facts in a short period of time, spotting the key info, and making good use of it. That said, it’s also obviously important to show basic people skills, like making eye-contact with the other people, or using their first name when addressing them (do memorise everyone’s names early on in the day).
That’s basically all there is to it. It’s really not about the maths at this stage, like I said, so don’t fret about the calculations, and instead focus on quickly finding key info, quickly forming an opinion, being able to back it up with solid arguments, and generally being a good team player.
Best of luck!