What is the airspeed velocity of an unladen swallow?

I take attendance by having the students answer a question.

This one might have been very cultural-reference-specific, but... I honestly want to know.

What is the airspeed velocity of an unladen swallow?

• African or European?

Okay, I deserved that. Other answers included:

• 2
• 3.00*10^8 m/s
• 3
• 50 minutes (one algorithms class)
• c=2.78*10^8 m/s
• 10mph
• 574mph
• -9.8m/s
• 5
• 12 knots
• 20mph west
• depends on mass of coconut
• 25mph, depending on African or European

I'm worried by the units (or lack thereof) on some of those answers.

And on a less quantitative level:

• What's an unladen swallow?
• as fast as it can dream
• The swallow is the center of the universe. All moves relative to it.
• very fast
• Will this be on the exam?
• faster than me
• impossible to measure

This post's theme word placentious (adj), "pleasing or inclined to please." The students are placentious indeed.