The answer is 20.
5*10-5*6=50-30=20
What problem is there to show work for?
Put a picture so we can see
None of them are irrational, the definition of an irrational number is a number that cannot be simplified, converted to a fraction, or has no pattern to it or is never ending. For example, a pi is an irrational number because it is never ending and has no pattern to it. Another example would be 0.21411446741354... irrational because it has no pattern to it and cannot be converted to a fraction.
Use the cone formula:
And so:

5654866.7 / 12000 = 471,
So the answer is 471 weeks.
Hope this helps.