Data Sufficiency (DS) | Standard Deviation Question

Hello,
I'm sorry I can't recall the exact wordings of the question I came across two days ago. I'm trying to reproduce the question from memory.

Q) Set A contains a,b,c,d. What is the standard deviation?

a) The mean of any two numbers taken from the set is 24.
b) The mean of any three numbers taken from the set is 24.

^^This is a data sufficiency question. I think the answer is 0 but I'm not sure. I'd also like to clear my Stats based concepts, please let me know if there are any resources
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