GST on aggregate or not?

I have  question as for my knowledge.

Lets say if a  registered trader makes following

1. Taxable Supply 2 lakh  a year

2. Interest from Bank FD 1 Lakh a year

3. Mutual Fund Profit 1 Lakh a year.

So Does he have to pay GST on 4 lakh or 2 Lakh?