76. A study of the nutritional value of a certain kind of bread shows that the amount of thiamine (vitamin B1) in a slice may be looked upon as a random variable with u = 0.260 milligram and o = 0.005 milligram. Accord- ing to Chebyshev's theorem, between what values must be the thiamine content of (a) at least 35 of all slices of this bread; (b) at least 143 144 of all slices of this bread