A 28-year-old primigravida at 39 weeks gestation presents to the labour ward with spontaneous rupture of membranes 6 hours ago. She is in active labour with contractions every 3 minutes lasting 45 seconds. On examination, cervix is 6 cm dilated, 80% effaced, and the fetal head is at −1 station. Vital signs are stable, and fetal heart rate is 140 bpm with normal variability. A partograph is plotted. Where should the alert line be drawn on the partograph for this patient?