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Explanation:

Here the critical points are 20, 60 and 100.

Case 1: n ≥ 100
⇒ n - 60 < n - 100
⇒ -60 < -100
This can never be true.
This case is rejected.

Case 2: 60 ≤ n < 100
⇒ n - 60 < - n + 100
⇒ 2n < 160
⇒ n < 80

Also,
- n + 100 < n – 20
⇒ 2n > 120
⇒ n > 60

∴ Possible integral values of n are 61, 62, 63, …, 79 i.e., 19 values

Case 3: n < 60
⇒ - n + 100 < - n + 20
⇒ 100 < 20
This can never be true.
This case is rejected.

∴ n can take 19 integral values.

Hence, option (d).