Original sentence: He then owned about 3,000,000 acres (12,000 km²).In 1900 he bought North Yanco and at great cost constructed about 200 miles of channels and irrigated 40,000 acres (160 km²)
Edited sentence: He then owned about 3,000,000 acres (12,000 km²).In 1900 he bought North Yanco and at great cost constructed about 200 miles of channels and irrigated 40,000 acres (160 km²)