help, help, quick poll

Here is one I’ve just realised I’ve got very wrong. I’m doubting myself on something very basic/obvious now, so a quick ask-the-audience please:

I have an old job description with 10 tasks.

I have a new job description with 7 tasks; 5 are the same as the old role, 2 are new.

What is the level of ‘job match’ for the new role?

A. 5/7 (surely not? why not?)

B. 5/10 (or is it?)

C. Some other calculation (my set theory is 40 years old, so no fancy intersections with chi squared lambdas please).

Vote A, B or C please and if you have time to show your working out…

Thank you all!