B-52 h/g question

[whistlingdeath77]

I was reading up on the B-52 and a certian mission during operation enduring freedom. The b-52 lost power to one engine but proceeded to the target with it's payload. After losing another engine they still decided to go and completed thier mission. My question about the B-52 h and g models are, how many engines can the b-52 lose and still be airborne? Empty and or with a decent payload,( doesn't have to be maximum.