Which formula shall I use?

Hello everyone, I have doubts in those 2 questions I would appreciated if anyone can give me some hints.
thank you in advance

1- What length-to-diameter ratio of screw would you choose for bakelite (a type of thermoset)?

2- . Calculate the MFI of a blend composed of 120kg polymer
A- having a MFI of 25 (g/10min) and 75kg of polymer
B- having a MFI of 8 (g/10min).