In the Following Proof, Which Justification Is Correct for Line

In the following proof, which justification is correct for line 6? $\begin{array}{llcc} \text { (1) \( (x) (U x \supset Y x) \cdot U a \) } & \text { \(/(\exists x) (\mathrm{Y} x \cdot \mathrm{U} x) \) } & \text {Fremise/Conclusion } \\ \text {(2) \( (x) (\mathrm{U} x \supset \mathrm{Y}) \) } && 1 \operatorname{Simp} \\ \text { (3) \( \mathrm{Ua} \) } &&1 \operatorname{Simp} \\ \text { (4) \( \mathrm{Ua} D \mathrm{Ya} \) } &&2 \mathrm{UI} \\ \text { (5) \( \mathrm{Ya} \) } &&3,4 \mathrm{MP}\\ \text { (6) \( \mathrm{Ya} \cdot \mathrm{Ua} \) } &\\\end{array}$

A) 5 Taut
B) 5 Simp
C) 5 Add
D) 3, 5 Conj
E) None of these answers are correct.