1. a : ℚ
2. b : ℚ
3. c : ℚ
4. c < 0
5. 0 < -(c)
⊢ uiff(a ≤ b;(c * b) ≤ (c * a))
{ Auto }
6. a ≤ b
⊢ (c * b) ≤ (c * a)
6. (c * b) ≤ (c * a)
⊢ a ≤ b