While performing a one-way ANOVA for classified data with three groups consisting of 10, 9, and 10 observations respectively, what are the residual/error degrees of freedom?

In a two-way ANOVA, the degrees of freedom for the error sum of squares is:

Arrange the following steps of ANOVA in the correct chronological order: A. Calculate mean sum of squares B. Set up null hypothesis C. Compute sums of squares (TSS, SST, SSE) D. Compare F-calculated with F-critical