Calculate the volume of excavation for a gutter with given dimensions, including converting units and finding the cross-sectional area.

Length of gutter ($L$) = $12 \text{ m}$
Top width of excavation = $15 \text{ cm} + 80 \text{ cm} + 15 \text{ cm} = 110 \text{ cm} = 1.10 \text{ m}$
Bottom width of excavation = $50 \text{ cm} = 0.50 \text{ m}$
Depth of excavation = $70 \text{ cm} = 0.70 \text{ m}$