If you buy a factory for $$250,000$ and the terms are $15$ percent down, the balance to be paid off over $15$ years annually at $8$ percent rate of interest, what is the total interest paid by the end of the $5$th year? need answer using the calculayor hp $10$bll$+$

This questin has already been answer however i dont understand the $3$rd step, which says the following: "determine the principal owed by the end of year $5($p$5)$ using the p$/$a formula again: p$5=$a$($p$/$a$,$ i$=8\%,$ n$=10)$

P$5=$$$24826\mathrm{.}38$ x $6\mathrm{.}71008$

P$5=$$$166587\mathrm{.}00$

i dont understand where the $6\mathrm{.}71008$ came from