I need to understand, have an exam tomorrow can you please answer with reasons and details, Question $12$:

Population $1$ has a mean of $7$ with a standard deviation of $1,$ and population $2$ has a mean of $6$

with a standard deviation of $2.$

a$)$ For population $1,$ what is $E(\stackrel{}{x})$ for samples of size $14?$

b$)$ For population $1$ what is the variance of the sample sum of samples of size $3?$

c$)$ For population $2,$ what is $E($sum$)$ for samples of size $4,$ where sum denotes the sample sum?

d$)$ For population $2,$ what is Var$(\stackrel{}{x})$ for samples of size $5$

I c