To bill customers for water usage, one city converts the number of gallons used into units. This relationship is represented by the equation u = 748g, where g is the total number of gallons of water used and u is the number of units.

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.