An aircraft reports at FL310 with an altimeter setting of 1013.2 hPa. If the local QNH at the nearest reporting station is 998 hPa, what is the aircraft's true pressure altitude relative to mean sea level (assuming 30 ft per hPa)?

1. 30,550 ft
2. 31,450 ft
3. 31,000 ft
4. 30,100 ft