Select the alternative that shares the same relationship with the third word as the second word shares with the first word. Rock : Music :: Lullaby : ?

Based on a certain logic, 'ZY5' is related to 'UT15'. Similarly, 'ML20' is related to 'HG30'. Following the same logic, to which of the following is 'RQ40' related?

Select the related letter pair from the given alternatives: HU : JW :: ?

According to a certain logic, 'ZY5' is related to 'UT15'. Similarly, 'ML20' is related to 'HG30'. Following the same logic, to which of the following is 'RQ40' related?