I just want to point out that there is small error in B. substitution. That confused me a little, so I actually checked it with the calculator.
(27.527 + 10.503 + 5.6534*2) / total_batches: While the formula is correct, the multiplication by two in the numerator is wrong. Also, the result (14.5612) is correct.
If the multiplication by two would be correct, the result should have been 16.44.
So, the correct substitution is: (27.527 + 10.503 + 5.6534) / total_batches
= (27.527 + 10.503 + 5.6534) / 3
= 14.5612