It says the answer must be one numerical value, it won't accept the interval I have put

The results below are based on a sample of 20 employees selected to study the relationship between income (Y, in $1,000) and four variables: Age (X1, in years), work experience (X2, in years), education (X3, degrees), of and number of past jobs (X4). Find the lower end point in a 95% confidence interval for the change in the mean salary in dollars, for a unit change in work experience, assuming that the other predictors remain unchanged. Note that normality is assumed for the multiple regression model. Standard Coeffcient Error Intercept -9.611198 2.77988638 Age 1.327695 0.1149193 Experience -0.106705 0.14265559 Educ 7.311332 0.80324187 PastJobs -0.504168 0.44771573