$($Related to Checkpoint $5\mathrm{.}5)($Solving for $n)$ Jack asked Jill to marry him, and she has accepted under one condition: Jack must buy her a new $$340,000$ Rolls$-$Royce Phantom. Jack currently has

$$54,000$ that he may invest. He has found a mutual fund with an expected annual return of $4\mathrm{.}5$ percent in which he will place the money. How long will it take Jack to win Jill's hand in marriage?

Ignore taxes and inflation.

The number of years it will take for Jack to win Jill's hand in marriage is years. $($Round to one decimal place.$)$