Consecutive 15 hour shifts, over 2 different weeks?

Can’t do it, as reduced rest periods count in the ‘working week’, not the ‘fixed week’, ie, between the end of one weekly rest and the start of the next.
Also, how can you work 3x15 without reducing rests? If you work 15 hours, then rest for 11 then you will start day 3 4 hours later than you started day 1, meaning in the 24 hour period from starting a shift, you will not be able to fit in even a reduced rest of 9 hours?

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