How do I calculate the total cost of a water purifier rental?
Add the payments for each pricing stage across the full agreement, then add any separate mandatory charges. Account for an advance payment according to the quotation so you do not count it twice.
Does a lower monthly price mean a cheaper plan?
Not necessarily. Compare the agreement length, the price after the promotion and any separate charges. Use the same comparison period and check that the models meet similar needs.
What if an advance payment is credited later?
Include it in the amount you need to pay upfront, but deduct the corresponding credit from the later payment when calculating the overall total. Confirm when and how the credit applies.