Choo Kheng must travel at least $288$ kilometers in a submarine in order to reach her destination.
Let $S$ represent the number of hours the submarine can travel on the water's surface and $U$ represent the number of hours it can travel underwater in order to reach Choo Kheng's destination.
$36S+64U \geq 288$
**The submarine travels for $2 \dfrac{2}{3}$ hours on the water's surface. What is the least number of hours the submarine must travel underwater in order for Choo Kheng to reach her destination?**
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