debt service coverage

CFA Level II Fixed Income
#1

i came across a question for debt service coverage using NOI/debt service does free operating cash flow + interest = NOI?

why are there are so many ways to say the same thing?!

#2

NOI = Net Operating Income

Source : Reading 46, LOS 46.f

#3

I know NOI is net operating income… im asking if net operating income is the same thing as free operating cash flow plus interest?