5. If price of an article decreases from P1 to Rs 25, quantity demanded increases from 900 units to 1200 units. If point elasticity of demand is 2 find P1?
9. The potential difference between the terminals of an electric heater is 60 V when it draws a current of 4 A from the source. What current will the heater draw if the potential difference is increased to 127.5 V ?