Match the following airlines with the countries where they are headquartered.
Airlines | Countries |
---|---|
1. AirAsia | A. Singapore |
2. AZAL | B. South Korea |
3. Jeju Air | C. Azerbaijan |
4. Indigo | D. India |
5. Tigerair | E. Malaysia |
What comes next in the series?
\(2, 6, 12, 20, 30, \ ?\)