How to create data.frame given the situations?

I am trying to create data.frame like in this picture i actually have a for loop before that

I got the values i wanted .

But when I tried to create data.frame, I faced error message ! what I have entered .

And when W is null as well.

All I wanted to do is to produce this:

Where I think I will also be using for loops to ensure quantity ordered equals to previous demand.

please help me.. I just started learning. thank you!!