I have a real-world problem.
Let $x$ = cost of goods
Let $f(x)$ be profit as a function of $x$.
I want to know the expression/solution for $f(x)$ such that:
$f(250) = 30$
$f(500) = 40$
$f(1000) = 50$
$f(2000) = 70$
$f(5000) = 200$
$f(10,000) = 300$
Is it possible to solve the expression/solution for $f(x)$? What's the answer? Show working out, please.
Now, I don't actually want a function that is too complicated or qualified such as a polynomial with too many terms. So even better as a solution, I want the simplest recognizable common function that would approximate this function.