(a) **GST amount:** $100
(b) **GST-exclusive price:** $1,000

### Working:
* **GST-exclusive price:** 
  $$\text{GST-exclusive price} = \frac{\text{GST-inclusive price}}{1 + \text{GST rate}} = \frac{\$1,100}{1.1} = \$1,000$$

* **GST amount:** 
  $$\text{GST amount} = \text{GST-inclusive price} \times \frac{1}{11} = \$1,100 \times \frac{1}{11} = \$100$$
  *(Or: $\$1,100 - \$1,000 = \$100$)*