Exercises 1 and 2 used different forecasting methods. Which method appears to provide the more accurate forecasts

Question:

Exercises 1 and 2 used different forecasting methods. Which method appears to provide the more accurate forecasts for the historical data? Explain.
In exercise 1

In exercise 2
Refer to the time series data in exercise 1. Using the average of all the historical data as a forecast for the next period, compute the following measures of forecast accuracy.