JNU SSS 2012 Question 39: Logic and proof techniques

$X$ is a positive integer satisfying the following conditions : (i) $50 \leq X \leq 79$ (ii) If $X$ is a multiple of 3, then $50 \leq X \leq 59$ (iii) If $X$ is not a multiple of 4, then $60 \leq X \leq 69$ (iv) If $X$ is not a multiple of 6, then $70 \leq X \leq 79$ Therefore, we can infer that