General form of the gravity model that economists typically estimate is given by: upper t subscript ij baseline equals upper a times startfraction upper y subscript i superscript a baseline times upper y subscript j superscript b over upper d subscript ij superscript c endfraction . empirical studies have found that the values of the exponents: 'a', 'b', and 'c' are very close to

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.

answer; ///(3) three parts;

answer; integrative;

answer; in the 1950s;