The rate of a unit per one. So for example 40miles/1hour. Hope it helped. :)
Seeing that this is over a year old i doubt this does you any justice but the answer is 4%
3/1 is the answer follow the line
The z-score for 36,000 is (36,000 - 40,000) / (15,000 / √25) = -1.333
The z-score for 42,000 is (42,000 - 40,000) / (15,000 / √25) = 0.6667
P(36,000 < x < 42,000) = P(-1.3333 < z < 0.6667)
P(z < 0.6667) - P(z < -1.3333)
0.7475 - 0.0913
0.6562
