Answer and explanation:
Given : The demand for a product for the last six years has been 15, 15, 17, 18, 20, and 19. The manager wants to predict the demand for this time series using the following simple linear trend equation : 
To find : What are the forecast errors for the 5th and 6th years?
Solution :
Data : 15, 15, 17, 18, 20, and 19.
The simple linear trend equation is given as, 
For t = 5 years



Observed 
Predicted 
Forecast error = Observed – Predicted = 20 – 22 = -2
Absolute forecast error = |-2| = 2
.
For t = 6 years



Observed 
Predicted 
Forecast error = Observed – Predicted = 19 – 24 = -5
Absolute forecast error = |-5| = 5.
It’s 121 feet bc 484 divided by 4 (because there’s 4 sides to a fenced area) is 121