Answer
8.77 hours approximately.
Work Step by Step
$\text{Speed}=\frac{\text{distance}}{\text{time}}=\frac{236\,miles}{4.6\,hours}\approx\frac{51.3\,miles}{hour}$
$\text{Time}=\frac{\text{distance}}{\text{speed}}=\frac{450\,miles}{51.3\,miles/hour}\approx8.77\,hours$
