I'm doing some data augmentation in my data.

Basically they look like this:

```
country.   size.   price.   product
CA.   1.   3.99.   12
US.   1.   2.99.   12
BR.   1.   10.99.  13

```

What I want to do is that because the size is fixed to 1, I want to add 3 more sizes per country, per product and increase the price accordingly. So, if the size is 2 then the price is price for 1 times 2, etc...

So basically, I'm looking for this:

```
country.   size.   price.   product
CA.   1.   3.99.   12
CA.   2.   7.98.   12
CA.   3.   11.97.   12
CA.   4.   15.96.   12
US.   1.   2.99.   12
US.   2.   5.98.   12
US.   3.   8.97.   12
US.   4.   11.96.   12
BR.   1.   10.99.  13
BR.   2.   21.98.  13
BR.   3.   32.97.  13
BR.   4.   43.96.  13

```

What is a good way to do this with pandas?
I'm tried doing it in a loop with `iterrows()` but that wasn't a fast solution for my data. So am I missing something?