the sound and some instances where the sound is traveling unobscured but other cases you don't. >> jeff, what do you think of that theory? >> that's certainly true in the case of air france as well. i know that they did not hear the pings, but the train there was very, i guess, mountainous is the way to say that underwater. so we know that the sea floor is not flat there. >> what's the longest you think those batteries could last, jeff? >> so our official answer is 30 days. the design margin is about 10% above that, and that's at the end of life or that's at the end of the six-year maintenance period. we do have design margin in it and there are varying efficiencies of the product, itself. so we feel, you know, 33, 35 days is not unreasonable to expect. but once it does reach that point, the intensity of the signal that it gives out will start to diminish. it will start to become more and