Net operating income (NOI) is a calculation used to analyze the profitability of income-generating real estate investments. NOI equals all revenue from the property, minus all reasonably necessary operating expenses.
The NOI is calculated as:

where:

Let us determine the revenue and expenditure.
Revenue:
There are 7 office suites, each with a potential annual rent of $9,000 each. Therefore, the total potential income on rent is:

The revenue from the vending machine is $3,000.
Hence,

Expenditure:
The vacancy is 8% of the expected rent. This is calculated to be:

Annual expenses are $25,000.
Hence,

NOI:
Therefore, the NOI is calculated to be:

The NOI is $35,960.
The SECOND OPTION is correct.