Assume there are four families in a country. The average per capita income of these families is Rs.5000. If the income of three families is Rs.4000, Rs.7000 and Rs.3000 respectively. What is the income of the fourth family?
Average capital income = Rs 5000
Income of 1st family = Rs 4000
Income of 2nd family = Rs 7000
Income of 3rd family = Rs 3000
Income of fourth family = 
5000 = 
20000 = 14000 + x
x = 6000
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