단위 변환 적용하기

# View the corn dataset
glimpse(corn)

corn %>%
  # Add some columns
  ___(
    # Convert farmed area from acres to ha
    farmed_area_ha = ___(___),
    # Convert yield from bushels/acre to kg/ha
    yield_kg_per_ha = ___(
      ___,
      crop = "___"
    )
  )