How long does it take for skin to replace itself

Throughout your life, your skin will change constantly, for better or worse. In fact, your skin will regenerate itself approximately every 27 days. Proper skin care is essential to maintaining the health and vitality of this protective organ

Explanation:

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.