It neve mentions how much of his farm he uses, but assuming he uses all of it area=base times height given base=4.2 height=3 area=4.2 times 3 area=12.6 square kilometers
11.6 rounded to the nearest whole is 12 and 4.1 rounded to the nearest whole is 4 (rule is if the decimal [or number in general] is 4 or lower, the whole stays the same and if the number is 5 or higher, the whole goes up by one). 12+4=16
