The answer adopted is wrong. Because: to subtract the joint of the upper cuboid and the lower cylinder (the upper bottom surface of the cylinder).

Paint area of each lighthouse:

1.2× 1.2×2+ 1.2× 1.8×4-3. 14×( 1.4/2)? +3. 14× 1.4×80

=2.88+8.64- 1.5386+35 1.68

=36 1.66 14 (square decimeter)

The 40 lighthouses * * * are: 361.6614× 40 =14466.456 (square decimeter).

14466.456 (square decimeter) =144.66456m2 ≈145m2.

1* * Labor cost: 6× 145=870 yuan.