Family Pension Calculation

My father was wb govt employee.He retired on 28-2-91 and drawn last month pension amounting Rs 13798 including 80 years benifit.He expired on 18-3-14. Now what will be the amount of my mother family pension ?
(Ropa 09) -3150×2.26=7119
(80years) 20% =1424
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Basic 8543
Feb'14--8543+4955+300=13798