Given the dataset

We start by computing the average:

We compute the difference bewteen each element and the average:

We square those differences:

And take the average of those squared differences: we sum them

And we divide by the number of elements:

Finally, we take the square root of this quantity and we have the standard deviation:

Answer: $15
Step-by-step explanation:
To find the markup price just multiply 30% by the amount.
30% * 50
0.3 * 50 = 15
The common number is 6.
72/6=12
60/6=10
12/10
simplify that, it is 6/5