This is a side related question, but I have always been curious about the process by which say, a Nikon team, decides to create a new lens. I'd love to know th

This is a side related question, but I have always been curious about the process by which say, a Nikon team, decides to create a new lens. I'd love to know things like what they trade off in terms of $, weight, complexity, aberrations, performance. And do they have to retire an old lens line to make room for a new one? And this is way too much to ask here (I'm sure I need to read an optics intro), but how in the world do they solve that they need 12 elements, etc. to make some aberration go away, by combining 3 different index of refraction glasses in a certain order, etc! Amazingly complicated. I imagine now there are ray tracing solvers for it, but I wonder how they did it in the early days of lens design!