Confused by general structure of website BUYPLSE

Is there a simple tutorial on how to use these modules? Like, am I supposed to build a function that returns the desired output? A class? None of the above?

If I could just see an example problem solved correctly, that would explain a lot.

I’m confused about how I know if I’ve done anything correctly. I’m on the very first problem BUYPLSE. My understanding of the problem is that I’m supposed to build a function that returns the sum total of the cost of purchased pens and pencils. I’ve tried inputting “2 4 4 5” in the custom input window, I’ve tried putting it at the top of the ide window, and creating an object and running a method that calculates the cost. I can hit “run” but nothing happens. Is there supposed to be a window that shows the console output? I can submit something, but I’m not sure what I’m supposed to be submitting.

def CalculateCost(payload):
    list = payload.split(" ")
    a = int(list[0])
    b = int(list[1])
    x = float(list[2])
    y = float(list[3])
    try:
        a <= 1 
    except Exception:
        valueerror("a is not less than or equal to 1")
    try:
        y <= 10**3
    except Exception:
        valueerror("y is not less than or equal to 10^3")
    output = a*x + b*y
    return output

CalculateCost(“2 4 4 5”)