Bottom-bottom perimeters are:
6: 1.5 = 4 (dm)
The bottom half of the bottom circumference is:
4: 2 = 2 (dm)
Width is:
2 - 1,2 = 0,8 (dm)
Double bottom surface is:
1.2 x 0.8 x 2 = 1.92 (dm2)
Total area is:
6 + 1.92 = 7.92 (dm2)
Answer: 7.92 dm2

Bottom-bottom perimeters are:
6: 1.5 = 4 (dm)
The bottom half of the bottom circumference is:
4: 2 = 2 (dm)
Width is:
2 - 1,2 = 0,8 (dm)
Double bottom surface is:
1.2 x 0.8 x 2 = 1.92 (dm2)
Total area is:
6 + 1.92 = 7.92 (dm2)
Answer: 7.92 dm2