prob stat: 2nd/2 parts. One sample has a mean of M=6 &

a 2nd sample has a mean of M=12. The 2 samples are combined into a single set of scores a)What is the mean for the combined set if both the original samples have n=4 scores b)What is the mean for the combined set if the first samples has n=3 & the 2nd sample has n=6? b)What is the mean for the combined set if the first samples has n=6 & the 2nd sample has n=3?