When 100 g of a liquid A at 100C is added to 50 g of a liquid B at temperature 75C, the temperature of the mixture becomes 90C. The temperature of the mixture, if 100 g of liquid A at 100C is added to 50 g of liquid B at 50C, will be :
(1) 80C
(2) 85C
(3) 70C
(4) 60C
