Si j'ai bien compris:
29min: 29*0.39 + 1.50 = 12.81E
30min: 30*0.35 + 1.50 = 12.00E
59min: 59*0.35 + 1.50 = 22.15E
60min: 30*(0.35 + 0.30) + 1.50 = 21.00E
90min: 30*(0.35 + 0.30 + 0.25) + 1.50 = 28.50E
120min: 30*(0.35 + 0.30 +0.25 + 0.20) + 1.50 = 34.50E