Mean Deviation about Mean for Continuous Frequency Distributions

Q. For two data sets $X$ and $Y$, each of size $5$, the means are given to be $2$ and $4$ and the corresponding variances are $4$ and $5$, respectively. The variance of the combined data set is
(correct answer + 1, wrong answer - 0.25)

1. $5.5$
2. $5.6$
3. $4.8$
4. $4.5$