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Just to make sure i was getting the same results as the guys in the first puzzle, i gave it a go and got pretty much the same answers. But i did it slightly differently which makes me question whether I've got this one right or not.... Anyways here it goes. (Assuming that Mr. D, Miss. S, lived at the same time, and when Mr. Z lived there, all three lived in the house at the same time... I think that's right)

Right, so i took $522.06 and divided it by the number of days which was 89, giving 5.86584.... 5.87 rounded.

5.87 * 41 = 240.49955.... Then divided that by 3, giving 80.1665... 80.17 rounded.

So as it stands,
Mr. D - 80.17 - 48days remaining
Miss. S - 80.17 - 48days remaining
Mr. Z - 80.17 - 0days remaining

I then took 5.87 * 48 = 281.5604.... then divided by 2, giving 140.7802.... 140.78 rounded.

I then added this to the 80.17's and was left with this...

Mr. D - 220.95
Miss. S - 220.95
Mr. Z - 80.17 + the 17.95 from the previous bill.

I wouldn't take my sums for it though until there's a second calculation.

41/89 = 0.46 (the fraction of the time you had 3 people living there)

0.46 * 522.06 = 240.15 (electricity bill while 3 people there)

240.15 / 3 = 80.05 (you each owe this for the 41 days)

281.91 / 2 = 140.95 (Mr D and Miss S owe this in addition to their 80.05)

Mr D: 221.00
Ms S: 221.00
Mr Z: 80.05

I lost a penny in the math there, so tack that on to Mr. Z I suppose and make him pay 80.06

EDIT: And there's a second calculation that's almost the same as mine, they just did the rounding in different steps and so our answers are off by mere pennies