1. **Problem:** Calculate the electricity bill for 180 kWh usage based on the tiered pricing system. 2. **Given tiers:** - 0 to 50 kWh: 1984 per kWh - 51 to 100 kWh: 2050 per kWh - 101 to 200 kWh: 2380 per kWh - 201 to 300 kWh: 2998 per kWh - 301 to 400 kWh: 3350 per kWh - Above 400 kWh: 3460 per kWh 3. **Approach:** Since 180 kWh falls into the third tier (101 to 200), calculate the cost for each tier up to 180 kWh. 4. **Calculations:** - Cost for first 50 kWh: $50 \times 1984 = 99200$ - Cost for next 50 kWh (51 to 100): $50 \times 2050 = 102500$ - Cost for remaining 80 kWh (101 to 180): $80 \times 2380 = 190400$ 5. **Total cost:** $$99200 + 102500 + 190400 = 392100$$ 6. **Rounding:** The problem asks for the result rounded to the nearest unit (thousand dong), so the final answer is 392100. **Final answer:** 392100 (thousand dong)