Asking idea for setting multiple automatic data picking logic!

If I wanted to add formula once I insert "Submit Date", I want "Go-live date(tentative)" date picker to automatically calculate and select date like this following example for the whole year:

For example:

- If i select from 1 May to 10 May then Golive date to be 20 Jun.

- if i select from 11 May to 10 Jun then Golive date to be 20 July.

- if I select 11 Jun to 10July then Golive to be 20 Aug. Please help me out for correct json formatting version coding to use in Microsoft Sharepoint List.