For the volume, look at the prism as a 12*10*20 rectangular prism with a smaller 5*6*20 prism cut out. Subtracting that gives a volume of 1800 cm^3.
For the surface area, we'll first tackle the L-shaped faces. As we did with the volume, we can think of these as 12*10 rectangles with a 5*6 rectangle cut out, so the area of each L-shaped face is 90 cm^2. In fact, the areas of the other faces are equal to the areas of the lateral faces of a 12*10*20 rectangular prism, which is a total of 880 cm^2. Adding, we have our answer of 2(90)+880=1060 cm^2.