For each value $$x$$ in a list of values with mean $$m$$, the squared deviation of $$x$$ from the mean is defined as $$(x-m)^2$$. The variance of the values in the list is the mean of the squared deviations.
For two lists of values. T and U, the numbers of values are equal and the means of the values are equal, but the variances of the values are distinct. List W consists of the values in T and the values in U combined.
Quantity A
The sum of the variances values in T and U
Quantity B
The variance of the values in W