Step 1: Side lengths
\(a=BC=3\), \(b=CA=4\), \(c=AB=5\).
Step 2: Incentre formula
\(I=\frac{aA+bB+cC}{a+b+c}\).
Step 3: Substitute
\(I=\frac{3(0,3,0)+4(0,0,4)+5(0,3,4)}{12}=\frac{(0,24,36)}{12}\).
Step 4: Result
\(I=(0,2,3)\), that is \(2\hat{j}+3\hat{k}\).
Final Answer:
The incentre is \(2\hat{j}+3\hat{k}\).
\[ \boxed{\text{(D) }2\hat{j}+3\hat{k}} \]