need help please

11. One sample has a mean of M = 5 and a second sample has a mean of M = 10. The two samples are combined into a single set of scores. a. What is the mean for the combined set if both of the original samples have n = 5 scores? b. What is the mean for the combined set if the first sample has n = 4 scores and the second sample has n = 6? c. What is the mean for the combined set if the first sample has n = 6 scores and the second sample has n = 4