Anew computer has a model number, a part number, and a serial number. the model number is assigned by the manufacturer to identify the type of computer. the part number identifies one part of the smaller components that make up the computer. the serial number is unique to each computer produced and identifies it. which relation is a function?

I would say all of them can be model as functions.

model number:
This would be a onto function, meaning that the outputs are not unique.
f(model_1) = f(model_2) = computer_type.

part number:
This would mean the function takes in multiple parameters.
f(part_1, part_2, part_3, ...) = computer

serial number:
This is the most obvious one; an one-to-one function:
f(s_num_1) = computer_1;
f(s_num_2) = computer_2;