Question 1180058
0.8212 is a z of +0.92 from invnorm (0.8212,0,1)ENTER or the table
0.92<(x-mean)/sd
so 9.2<x-mean or 282.5-mean
so mean is 273.3 sec 
-
 z>(258.3-273.3)/10 or >-1.5
that probability is 0.9332

mean is 273.3
mean -1 sd is 263.3
mean-2 sd is 253.3
Mean +1 sd is 283.3