What does president obama consider one of the most serious economic and national security challenges facing the us today\?

Cyber Threat. During the regime of President Obama there was the incident of North Korea hacking Sony Picture entertainment and the release of a yet unrealised movie which sony had spent millions of dollars on into several torrent sites and other internet sources. This incident gave just one instance of what could happen if hackers get into the US financial system or the electricity or even defence. President Obama published an article on the dangers of hackers getting into the daily and regular systems which Americans are used to like the banking system or the electricity and he called for white house to have a bill to tackle this. His thoughts on this was in the white house website and later published in the wall street journal

Cuneiform (a type of writing)

They weaken the south vietnamese army.