Answer:
a, b, and c are close to +1
Step-by-step explanation:
The gravity model is characterized as the model of international trade which helps in predicting the flow of bilateral trade on the basis of economic sizes, as well as, the distance between two units. The empirical studies have lately discovered that the values of the exponents in the formulae while determining the 'volume of trade from country i to country j' would be close to +1.'