Hi there , very new to ZA sop forgive me if this seems simple !?

I have an imported table accounting entries with one column in the table being "Account Code" 

I have added a new column ("Account Group" which I would like to contain derived text (being either "P&L" ..Profit and Loss or "BS"... Balance sheet) depending on whether the numerical value in the "Account code" field is a value up to 3999 in which case the derived text for that record needs to be "BS" or above 3999 in which case the derived text for that record  will be "P&L" 

Hopefully that makes sense , any advice on the formula required in the "Account Group" column woudl be much appreciated 

Thanks

J