Final answer:
After a fall in price that increased demand for Good X from 300 to 400 units and decreased sales revenue by £400, the new price of Good X is calculated to be £2 per unit.
Step-by-step explanation:
The question asks us to calculate the new price of Good X after its demand increased from 300 units at £4 to 400 units as a result of a price fall, and knowing the sales revenue fell by £400. To find the new price, we need to use the information about the changes in quantity demanded and sales revenue.
Initial revenue was 300 units × £4 = £1200. The sales revenue decrease by £400 implies the new revenue is £1200 - £400 = £800. With a demand of 400 units at the new price, we calculate the new price by dividing the total sales revenue by the quantity demanded: £800 ÷ 400 units = £2 per unit.
Therefore, the price of Good X after the fall is £2.