On its 2019 income statement, AT&T reports a 7.2 percent increase in revenue from $152 billion in 2018 to $163 billion in 2019. Yet net income dropped by 28 percent from $19.4 billion to $13.9 billion. Interestingly, a line item on the statement entitled "other income" was positive $6.8 billion in 2018 and negative $ 1.1 billion in 2019. Explain the difference between net operating income and "bottom line" net income, and its implication in situations like this.