As a risk management consultant at KPMG, my team had to perform the risk vs reward scenarios for banks. The advent of derivatives (and in particular complex options) combined with exposure in foreign currencies meant that this was no longer a task the 'bank manager' could perform on the back of an envelope. With others, I developed computer risk models and for a few years KPMG was 'ahead of the game' Eventually they sold out the idea to JP Morgan who along with others developed the complex risk models used today.

Guys like The Donald have access to the same risk engines the banks use. They can determine which 'numbers' to give the bank to get the right answer 'spilled out' the other end!