Present value Factor

Having some trouble figuring out how the present value factor was derived in a sample problem, maybe you guys can help me out. “Consider 1yr Libor swap with quarterly payments priced at 6.052% at initiation when 90-day LIBOR was 5.5%”. The problem then shows 60 day libor to have a rate of 6% and a PV factor of 0.99010 150 day libor to have a rate of 6.5% and a PV factor of 0.9763 240 day libor to have a rate of 7% and PV factor of 0.95541 In this question the PV factor is given, but how do they derive these numbers? (i’m looking at a schweser problem on page 284 of derivatives book)

1/(1+(r*day/360)) = PV factor eg 1/(1+(.06*60/360)) = 0.99010

Thanks