Question 907665
z = (x-m)/sd
x = 700 = price of 250 computers that were produced at that price or below.
m = 1400 = average price of all computers that were produced.
sd = 250 = standard deviation of all computers that were produced.


z = (x-m) / sd = (700 - 1400) / 250 = -700/250 = -2.8


z = -2.8


look up in the z-score table to see that a z-score of -2.8 has .00256 * area under the normal distribution curve to the left of it.


this means that .00256 of the computers were sold at a price at or below 700.


since there were 250 of them, then the total number of computers had to be 250 / .00256 = 100,000 computers were sold in all.


the actual answer you get will be determined by rounding.


some charts will show the area to the left of a z-score of -2.8 as .0026.


some calculators will be more accurate and show the z-score of -2.8 as .0025551906...


your answer will be somewhere around 100,000.


the z-score table i used is shown below:


<a href="https://www.stat.tamu.edu/~lzhou/stat302/standardnormaltable.pdf" target = "_blank">https://www.stat.tamu.edu/~lzhou/stat302/standardnormaltable.pdf</a>