Final answer:
The question involves estimating the sum of large numbers by rounding each to the nearest thousand and then adding them together. After rounding, the total estimate is approximately 10,000, so the closest answer without exceeding this amount is option (a) 8000.
Step-by-step explanation:
The question asks for an estimation of the sum of several large numbers. When estimating large numbers, we can round each number to its nearest thousand or other significant figure depending on the required estimation precision. In this case, we could round each number to the nearest thousand to make the addition easier.
Let's round each number: 623 rounds to 0 (since it's less than 500, we round down to the nearest thousand), 2777 rounds to 3000, 1220 rounds to 1000, and 5834 rounds to 6000. Adding these rounded numbers together, we get 0 + 3000 + 1000 + 6000 = 10,000.
Therefore, a reasonable estimate for the sum of the numbers provided would be 10,000, which corresponds to option (a) 8000, this is closest to our calculation without going over, providing the best estimate.