So how does the amount spent on wages remain constant with the workday being extended? Would this not just appear as additional labour performed for free or a reduction in wages?
For example if an 8-hour workday consisting of 4 hours necessary and 4 hours surplus labour,
80c + 5v + 5s
is extended to a 12-hour workday, now with 4 additional surplus-labour hours (production of absolute surplus-value),
80c + 5v + 10s
how does the amount spent on wages remain constant here? I'm guessing this might be answered somewhere in vol. 1. The relevant passage is this:
The increase of absolute surplus-value, or the prolongation of surplus-labour, and thus of the working-day, while the variable capital remains the same and thus employs the same number of labourers at the same nominal wages [...]