Welcome Julie,
Firstly, I seriously doubt you will get 12L14 in tube form, but in the make-believe world of TV, I guess it can be conjured up. With it's high Lead content, the 12L14 steel is known for it's free machining qualities and is not a good structural or load bearing material. Given that, Grade 8 bolts to affix 12L14 to anything would be like using a two-handled cast-iron spoon to eat ice cream.
Next, we would need to know the load applied, the supports and the direction of the loads and stresses to be able to even offer a hint.
If this really-is for TV make-believe then why do you need to work the Math?
I have yet to be convinced that this is not homework.