What is the highest mountain in Iceland?

What is the highest mountain in Portugal? What is the highest mountain in Slovenia? What is the highest mountain in Bulgaria? What is the highest mountain in Romania? In which country is most of the Namib Desert located? In which country is most of the Negev Desert located? In which country is most of the Simpson Desert located? In which country is most of the Rub' al Khali (Empty Quarter) located?