An oil refinery is located on the north bank of a straight river that is 2 km wide. A pipeline is to be constructed from the refinery to storage tanks located on the south bank of the river 6 km east of the refinery. The cost of laying pipe is $400,000ykm over land to a point p on the north bank and $800,000ykm under the river to the tanks. To minimize the cost of the pipeline, where should p be located?.