Progressive waves — practice question

A wave with amplitude $a$ has intensity $3.0\,\text{W m}^{-2}$. What is the intensity of another wave with the same frequency but amplitude $2a$?

• A$4.2\,\text{W m}^{-2}$
• B$6.0\,\text{W m}^{-2}$
• C$9.0\,\text{W m}^{-2}$
• D$12\,\text{W m}^{-2}$