i need help on solving the following practice problem for statistics

a. There are nine data points and error terms. The following is the first 8 of 9 error terms or residuals. What is the numerical value for the ninth residua -15.7, -8.0, -1.6, +11.8, +24.3, +12.7, -1.9, -7.5, _? b. Using the answer to part "a", If we saw a regression equation and noticed the following residuals what analysis can be made? Be specific in terms of the type equation involved and the signs of the coefficients