**G1:** $110,000  
**1A:** $10,000  
**1B:** $6,000  
**W2:** $8,000  
**Net amount payable:** $12,000  

Working:  
- G1 = total sales (GST-inclusive) = $110,000  
- 1A = GST on sales = $110,000 ÷ 11 = $10,000  
- 1B = GST on purchases = $66,000 ÷ 11 = $6,000  
- W2 = amounts withheld from wages = 20% × $40,000 = $8,000  
- Net amount payable = (1A − 1B) + W2 = ($10,000 − $6,000) + $8,000 = $12,000