Newton interpolation - Answer mismatch

**Hi,**

I am trying to solve this question but always my answer is mismatching with the answer written in the book. Can anyone help to solve this question so that i can verify the answer.

Q: From the table(shown below), using the newton interpolation formula, estimate the number of students who abtained marks between 80 - 85

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Marks ..................__| 40 - 50 | 50 - 60 | 60 - 70 | 70 - 80 | 80 - 90|__

No. of Students......|....40....|.....78....|.....10...|.....3......|....19...|

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Need help asap.

Thanks in advance

Lalit Chugh