roger mika stepped away. we will will go door independent line, nick is waiting in oakland california. good morning. >> caller: hi. i was noticing in technologies you mentioned wind and solar. i've been puzzled for some time why tidal energy hasn't been exploited. it's available and most of the people in the united states live within 25 miles of the coast. it's an obvious of energy and easy to use. >> guest: it's a great question. the answer is unfortunately like in a promising sounding alternative energy that has to be economical and tidal energy is useful and could be promising but it's not yet economical. it's just not going to generate enough power to be worth installing the installations and doing what you need to do to harness the power. that's actually what's interesting about this item on our list about smart wind and solar power. the knock against solar and wind is that it is too not cost competitive with coal or natural gas power. what's interesting about this item is that the utility in colorado in