12x12x10. What is the hole being used for? i'm with the previous poster on type of soil, sloping etc. I use heavy equipment at my job, and my tractor at home. I wouldn't consider digging with the backhoe on a CUT to 10'. In theroy you could do it, but you'd be piling your dirt, and then moving it with the FEL to get it out of the way. Unless your working in heavy clay that will hold near vertical sides, your hole just grew to 22x22x10 to have your 1/1 safety slope. if you figure how much more dirt that is to move, your talking alot of hours.
If the bottom needs to be near flat, (ie a building slab) then you've got another set of tools and requirements.
In any event, unless you've got endless time and boundless energy, i'd hire someone with a large track hoe, they would have that hole dug in under 2 hours tops.
then you can go play with the dirt piles!