1. The problem states that a number $g$ is rounded to the nearest integer 80. 2. a) To write down the error interval for $g$, note that when rounding to the nearest integer, $g$ lies within half a unit above or below 80. 3. Therefore, the error interval is $$79.5 \leq g < 80.5$$. 4. b) To check if $g$ can be 79, observe that 79 is outside the error interval $[79.5, 80.5)$. 5. Since 79 is less than 79.5, $g$ cannot be 79 after rounding to 80. 6. In conclusion, the value of $g$ cannot be 79; it must be within the interval where rounding leads to 80.