> PV of interest payments. (Bonds)?

PV of interest payments. (Bonds)?

Posted at: 2014-12-05 
here's the Excel formula

= NPV (0.06, 42000, 42000, 42000, 42000, 42000, 42000, 42000, 42000, 42000)

Principal Amount of bonds: 600,000

Stated interest rate: .07

Effective (market) interest rate: .06

Number of interest periods: 9

Price Computation:

PV of Principal [ use PV function]: 355139

PV of interest payments [use PV function]: 285671, BUT HOW DO I CALCULATE THIS?

Total: 640810

I am given the correct answer of 285671 but I have no idea how they got that number.

Please help, and thank you!