Table: moldova_geography
Columns: land_formation
area_km
of_which_currently_forests_km
forests
habitat_type

Question: When middle prut valley is the land formation what is the highest of which currently forests, km² ?
SQL: SELECT MAX("of_which_currently_forests_km") FROM moldova_geography WHERE "land_formation" = 'Middle Prut Valley'

Question: When 312 is  of which currently forests, km² what is the land formation? 
SQL: SELECT "land_formation" FROM moldova_geography WHERE "of_which_currently_forests_km" = 312