An oil refinery is located on the north bank of a straight river that is $2\text{km}$ wide. A pipeline is to be constructed from the refinery to storage tanks located on the south bank of the river $8\text{km}$ east of the refinery. The cost of laying pipe is $\$300{,}000\text{/km}$ over land to point $P$ on the north bank and $\$600{,}000\text{/km}$ under river to the tanks. What is the minimal cost to construct a pipeline from the refinery to the storage tanks?

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