known: EF = km
AB = 4 km FG = 3 km
BC = 4 km GH = 4 km
CD = 3 km HI = 4 km
ED = 4 km BI = 3 km
HB = CG = (3 + 4)km = 7 km
Area l = Area △ ABI
Area I = 1/2 * AB * BI
= 1/2 * 4 * 3
= 6 km^2
Area II = Area ▭ BC GH
= BC * CG
= 4 * 7 = 28 km^2
Area III = Area ▭ CDEF
= CD * DE
= 3 * 4 + 12 km^2
Area 1 = 6 km^2
Area 2 = 28 km^2
Area 3 = 12 km^2
Total = 46 km^2
