center-pivot irrigation

1.  Use the figures below to estimate the area of the center-pivot irrigation (CPI) fields in 1991, 2000, and 2004. CPI-irrigated fields appear as green circles on the satellite images. Each circle covers approximately 0.166 km²  (1/6 km²).  For this question, we will focus on the study area outlined in black in each of the three images.

a.  How much land was irrigated in the black square in 1991?  ________km²

b.  How much land was irrigated in the black square in 2000?  ________km²

c.  How much land was irrigated in the black square in 2004?  ________km²