An electrical firm manufactures a​ 100-watt light​ bulb, which, according to specifications written on the​ package, has a mean life of 700 hours with a standard deviation of 70 hours. At​ most, what...

An electrical firm manufactures a​ 100-watt light​ bulb, which, according to specifications written on the​ package, has a mean life of 700 hours with a standard deviation of 70 hours. At​ most, what percentage of the bulbs fail to last even 350 hours? Assume that the distribution is symmetric about the mean.

According to​ Chebyshev's theorem, at most ___% of the bulbs fail to last even 350hours.