4. Calculate the price elasticity of the demand if the price increased from 20 to 22 PLN/kg. and consumption decreased by 6%. Is the demand elastic or inelastic? Give several reasons for such elasticity.

5. Buyers of the product A can be divided into two groups. There are 2000 buyers in group 1 and 700 buyers in group 2. The income elasticity of the demand for group 1 is 0.5, and for group 2 is -1,4. Economists predict that during the next year incomes on average will grow by 4%. Each buyer currently purchases 3 kg of product A. Calculate, how will the producer's revenue change if the current price is 2 PLN/kg.

6. Two goods have been connected. Researchers discovered that if the price of the good A increases by 6%, the consumption of the good B will decrease by 4%. What type of connection is between them?