R1, R2, R4: Suggest more extensive analysis on Assumption 2 and the normalization step in Algorithm 1

We would like to thank the reviewers for their insightful feedback. In the following, we address their key concerns. Following reviewers' suggestions, we will add more thorough analysis in the final paper. Its advantages and applications are then limited. Mixup was introduced in VPU as a regularizer to solve the overfitting problem (Table 4 and Lines 100-105, 376-384).