answer with explanation

3. A drilling rig 22 km offshore is to be connected to a refinery onshore, 38 km down the coast from the rig as illustrated. If underwater pipe costs $25 000 per km and underground pipe costs $18 000 per km, how far down the coast should the underwater pipe be routed to give the least expensive connection? [5] Rig Water 22 km Refinery Land 38 km