The answer is B, you should really learn how to calculate these yourself though because they come up a lot.
Answer: 505
Step-by-step explanation:
The formula to find the sample size n , if the prior estimate of the population proportion (p) is known:
, where E= margin of error and z = Critical z-value.
Let p be the population proportion of crashes.
Prior sample size = 250
No. of people experience computer crashes = 75
Prior proportion of crashes 
E= 0.04
From z-table , the z-value corresponding to 95% confidence interval = z=1.96
Required sample size will be :
(Substitute all the values in the above formula)
(Rounded to the next integer.)
∴ Required sample size = 505
You subtract the numbers 7,801 and 4890
The answer is 2,911
I have included attachment below
so since a rhombus is 2 pairs of paralell sides, we can cut it into 4 triangles
we can see that we can take the bottom 2 triangles and put them on top to get a rectangle that is width 21 and height 32/2 (16=height
area of rectangle=legnth times width=16 times 21=336 m^2
answer is 336 m^2