BDY to HPY calculation having, trouble, example, convert, something

wonderfuldream

I"m having trouble figuring out converting BDY to HPY

The schweser book states that you can convert BDY to HPY by
RBD(days/360) / 1 - RBD (days/360)

So for an example
Tbill priced at 98,500
Face Value: 100,000
120 Days until maturity

RBD is calculated as 1500 / 100,000 * 360 / 120 = 4.5%

Now the HPY calculation from this 100,000 / 98,500 = 1.5228%

but when I try to convert BDY to HPY as stated in the book
RBD(days/360) / 1 - RBD (days/360), I get 4.713%

Am i missing something from this calculation?