Explanation:

- Step 1: Determine Sue's cost price.

- Rima buys the watch for Rs 2,178 at a 10% profit for Sue.

- Let Sue’s cost price be x.

- x * 1.10 = 2,178, hence x = 2,178 / 1.10 = 1,980.

- Step 2: Determine John’s cost price.

- John sold to Sue at a 20% profit, so let John’s cost price be y.

- y * 1.20 = 1,980, hence y = 1,980 / 1.20 = Rs1,650.

- Correct Answer: Option 1 – 1,650.

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