How in Scriptrunner set value for select list(single choice) Behaviour

[Alex]

Hello Atlassian community! I really need your help. I'm trying to set the value of a field depending on the selection in another field. I use "Behavior"  but none of the options found on the Internet solved my problem.

I have two fields: "CPU" and "RAM". My task: depending on the choice in cpu, automatically substitute the value in ram.

if value in 

cf_CPU: =  2 

cf_RAM: 

(list options)

2,

4,

8

if value in 

cf_CPU: =  4

cf_RAM: 

(list options)

4,

8,

16