A manager at a local bank analyzed the relationship between monthly salary and three independent variables: length of service (measured in months), gender (0 = female, 1 = male) and job type (0 = clerical, 1 = technical). The following ANOVA summarizes the regression results: Df Ss Ms F Regression 3 1004346.771 334782.257 5.96 Residual 26 1461134.596 56197.48445 Total 29 2465481.367 56197.48445 Coefficients Standard Error T Stat P-Value Intercept 784.92 322.25 2.44 0.02 Service 9.19 3.20 2.87 0.01 Gender 222.78 89.00 2.50 0.02 Job -28.21 89.61 -0.31 0.76 In the regression model, which of the following are dummy variables? (a) Intercept (b) Service (c) Service and gender (d) Gender and job