Вычислите, выбирая удобный способ:

• a) 25 × 289 × 4 = (25 × 4) × 289 = 100 × 289 = 28900
• б) 8 × 971 × 125 = (8 × 125) × 971 = 1000 × 971 = 971000
• в) 50 × 93 × 20 = (50 × 20) × 93 = 1000 × 93 = 93000
• г) 400 × 34 × 500 = (400 × 500) × 34 = 200000 × 34 = 6800000