Answer:
$54.35
Step-by-step explanation:
The differences from the average value are ...
2.60, 5.00, -1.75, -4.25, -0.95
The total of these differences is +0.65, so the final bill must have a value that is $0.65 lower than the average.
The bill for the 6th month is $54.35.
_____
Check
The average of the bills for 6 months is ...
(57.60 +60 +53.25 +50.75 +54.05 +54.35)/6 = 330/6 = 55
