I want to know the answer to the following question:
What agreement did Liberia sign n 2006?
All the background I'm provided with is that "Following the inauguration of the Sirleaf administration in 2006, Liberia signed several multibillion-dollar concession agreements in the iron ore and palm oil industries with numerous multinational corporations, including BHP Billiton, ArcelorMittal, and Sime Darby.". Is that enough to answer the question?