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

**Working:**
- The GST-inclusive price equals the GST-exclusive price × 1.1.
- GST-exclusive price = $1,100 ÷ 1.1 = **$1,000**
- GST = $1,100 − $1,000 = **$100** (equivalently, $1,100 ÷ 11 = $100)