Gan oil refinery is located on the north bank of a straight river that is 3km wide. a pipeline is to be constructed from the refinery to storage tanks located on the south bank of the river 8km east of the refinery. the cost of laying pipe is $700,000/km over land to point p on the north bank and $1,400,000/km under river to the tanks. what is the minimal cost to construct a pipeline from the refinery to the storage tanks?