Answer 1

Not sure if you're trying to reference a min() function here or not.
https://www.geeksforgeeks.org/stdmin-in-cpp/

But this exercise from c++ occurs before "functions" are taught.

In the case of your code, min is never declared, for example
double min; or double min = ...

If you want a clue as to how to solve this look at practice 32.2