Algebra-Using The Product Rule With Multiple Variables

I HATE using the product rule with mutiple variables online. I had to do this one problem and it went exactly like this:
4c^6(w^7)(20c^9)(w)
and then I simplified it with the product rule and here's what it simplified out to
80c^15(w^7)(w)
I clicked on "Done" and it said I was not finished the problem. So, I simplified it again and again until I had simplified eight times. And it stayed 80c^15(w^7)(w). If I had made a mistake, the expression would have been outlined in red. But the program is saying it's right, I just need to keep simplifying until I'm dead and gone.
Maybe it's me, or maybe it's the program. I have no idea. But I really hate using the product rule with multiple variables.