Economics of an M&A deal

Hi everyone. I'm a first year IB analyst at a MM bank working primarily with M&A deals. Basically, I have trouble understanding what the actual PnL of an IB department looks like and, therefore, how the bank makes money and distributes bonuses. The bonus system at my bank is not very transparent - which is normal, I guess, but I'd like to understand what's the range I should be expecting / asking for given my performance. Plus it's always good to understand the MD's perspective.

Let's take a hypothetical example - a small team of 1 MD, 1 sr. associate, and 1 analyst lead and close a deal of ~$50 mln. The bank then takes 3% commission of ~$1.5 mln, which is its revenue. For the sake of simplicity, let's say that these 3 do not work on any other deals. How would the revenue and bonuses be distributed?

Obviously, there are additional expenses, like back-office support, office rent. The IB division is also a small part of the bank, so I guess they should share some of the profit with partners from other divisions? For context - this takes place in a developing European economy, the bank is local. My annual base is $10k after taxes, and overall (not in IB, but in my country), salaries of $36k+ net are considered high (and if you make $120k, you are basically rich by most standards).

Thanks