Forcasting

The following information relates to questions 18 and 19:
The following variations and trend have been calculated for sales over a period of time using the additive model:
Seasonal
variation
Quarter 1 +25
Quarter 2 –10
Quarter 3 –30
Quarter 4 ?
Trend +50 per quarter
The last known trend reading was taken in year 3, quarter 3 and was £1,750.
18 What would be the seasonal variation for quarter 4?
A +15
B –15
C +35
D –35
19 What would be the time series value for year 4 quarter 3?
A £1,950
B £1,920
C £1,900
D £1,870