We have now found that the heating formula for the metal bar is as follows.

$T=-85e^{ln(\frac{83}{85})t}100$

We are asked to solve for the tirne $l$ at takes for the metal bar to reach $75C.$ To do so$,$ let $I=75$ and solve for $4,$ rounding the final result to one decimal place.

$r=-8ln\frac{E}{n}5y100$

$75=-85ln(\frac{83}{85})t100$

$=e^{ln\frac{80}{85}}t$

Therefore, how long $($in seconis$)$ will it take the bar to reach $75C$ under the given conditions? $($Round your answer to one decimal place.$)$

$$ sec$.$