Ask HN: General Formula to choosing a language

I am speaking at a talk "What programming language should I choose" and thought would be funny to have a formula to convey the meat of it. Am I missing something or do you have a better formula?

f(x) = (context * times) - financial net

context = what are you working on

times = how current is the language, are there newer better ones or are their current versions unstable

financial net = will this help you find a job or do you need a job ASAP