The system of equations \( 2x + 3y + 5z = 9 \); \( 7x + 3y - 2z = 8 \); \( 2x + 3y + \lambda z = h \) have a unique solution ____ .
An electricity utility company charges ₹7 per kWh. If a 40-watt desk light is left on for 10 hours each night for 180 days, what would be the cost of energy consumption? If the desk light is on for 2 more hours each night for the 180 days, what would be the percentage-increase in the cost of energy consumption?