A researcher tests for structural stability in the following regression model:

$y_t = \beta_1 + \beta_2 x_{2t} + \beta_3 x_{3t} + u_t$

The total sample of 200 observations is split exactly in half for the sub-sample regressions. Which would be the unrestricted residual sum of squares?
(A)The RSS for the whole sample (B)The RSS for the first sub-sample (C)The RSS for the second sub-sample (D)The sum of the RSS for the first and second sub-samples
D