Answer:
a and c
Step-by-step explanation:
in answer a 390 is 383 rounded up and 450 is 449 rounded up so 840 would be a correct estimated
in answer b 400 is not a good round-up for 383 since it is far out of reach of 383 and 449 so be is an incorrect estimate
in answer c 380 is a great round-down for 383 because its only 3 numbers less then 383 and 450 is good too so this is a correct estimate
in answer d we have a good estimate for 449 but not 383 because the rounded version is not near 350 so this is an incorrect estimate
in answer e the estimates are way to low and to not serve as a good estimate
