The price of a table lamp is lowered from $30 to $20, which causes the quantity sold to rise by 10%. Using the midpoint method, the price elasticity...

The price of a table lamp is lowered from $30 to $20, which causes the quantity sold to rise by 10%. Using the midpoint method, the price elasticity of demand is: 1.4.00 2.1.00 3.0.50 4. 0.25 5. 0.05. I know what the midpoint method is, but i have no idea how to do this. could you please help me do a step by step? I have test tmm