Technical Question/ How to choose the lowest value from several fields in a record?

Hi there- I am new to Ninox and was wondering if anyone had any bright ideas- I basically want to just choose the lowest of three fields that are prices of the same item form different suppliers and return the product code? I apologise if this is blindlingly obvious!! Thers is an image below of an example record to helpexplain what i mean.

Many thanks in advance

Alex