Which of the following is equal to -18

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.

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.

Y= a(x-3)squared-1 what is the value of a