graphing calculator is recommended oil refinery is located 1 km north of the north bank of a straight river that is 3 km wide A pipeline is to be constructed from the refinery to storage tanks located on the south bank of the river 9 km east of the refinery The cost of laying pipe is 2 er land to a point P on the north bank and 400 000 km under the river to the tanks To minimize the cost of the pipeline how far downriver from the refinery in km should the point P be located Round your answer to two decimal places km