**(a)** $100  
**(b)** $1,000  

**Working**  
GST-inclusive price = $1,100  
GST rate = 10%  

GST fraction of total = \( \frac{1}{11} \)  
\[
\text{GST amount} = \frac{1{,}100}{11} = 100
\]  

GST-exclusive price = total − GST  
\[
1{,}100 - 100 = 1{,}000
\]  
(or \( \frac{1{,}100}{1.1} = 1{,}000 \))