In this expression, solve the multiplication in the parenthesis.
-5×p×4×z×6×u
since multiplication is commutative,
-5×p×4×z×6×u=-5×4×6×p×z×u= -120pzu
Now multiply this by 3.
(-5p4z6u)3 = (-120pzu)3 = -360pzu
Every confidence interval has associated z value. As confidence interval increases so do the z value associated with it.
The confidence interval can be calculated using following formula:

Where

is the mean value, z is the associated z value, s is the standard deviation and n is the number of samples.
We know that standard deviation is simply a square root of variance:

The confidence interval of 95% has associated z value of <span>1.960.
</span>Now we can calculate the confidence interval for our income: