In a particular geographical area, the demand function for each person i for a particular good is qi^d=100+0.2ii-9p

where qid is quantity demanded for person i, ii, is person i's income, and p is the commodity's price. (note that p is constant across individuals, since all individuals face the same price. therefore no i subscript is needed.) for the firms in this area the supply function for this good is

qsj = -50 + 20 p

where qjs is the quantity supplied of the good by firm j. (note that a different subscript is needed. why? )
there are 5 firms and 100 consumers. total income of the consumers is $100,000. equilibrium occurs where

100 5
î£ qid= î£qjs
i=1 i=1
(i. e., market demand equals market supply). find the equilibrium price.