A submarine is fitted with circular windows with diameter $0.30\,\text{m}$. These windows may withstand a greatest external pressure of $660\,\text{kPa}$ before they crack. Calculate the least external force required to crack the windows?
- A$47\,000\,\text{N}$
- B$190\,000\,\text{N}$
- C$310\,000\,\text{N}$
- D$620\,000\,\text{N}$