求助，两道数学题

koine

1、70.75.80,85,90,105,105,130,130,130
the list shown consists of times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 meter, if the standard deviation of the 10  running times is 22.4 seconds, rounded to the nearest tenth of a second ,how many of the 10 runing times are more  than 1 standard deviation below the mean f the 10 running time?
A 1 B2 C 3 D4 E 5
2 IS X^4 +Y^4>Z^4
(1) X^W+Y^2>Z^2
(2) X+Y>Z