I spent 1 hour each on tasks 1 and 2.

Task 4: A Dataframe can contain one or more Series, or a Dataframe is a collection of Series. Time taken: 30 seconds

Task 5: I would explain to the student that the logic is mostly correct but that the indentation of the return statement in their solution implies that the function will return prematurely. I would demonstrate this by stepping through the function manually with the student. Time taken: 30 seconds

Task 6: 2^2*2+3^2*3.5-2*2*3*0.8 = 29.9. Time taken: 1 minute

Task 7: Omer: (0.5^2*400+0.7^2*100)/500 = 0.298 . Limor: 0.287856072 Time taken: 1 minute