in an A. P the difference between the 10th and 6th terms is 60 and the 10th term is 22/3 times the 6th term. what is the common difference and the first term of the sequence

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.