contour plot of a custom function in R - Stack Overflow

I'm working with some custom functions and I need to draw contours for them based on multiple values for the parameters. Here is an example function: I need to draw such a contour plot: Any idea?

contour plot of a custom function in R - Stack Overflow

contour plot of a custom function in R - Stack Overflow

contour plot of a custom function in R - Stack Overflow

contour plot of a custom function in R - Stack Overflow