In a certain code language, 'x' represents '+', '÷' represents 'x', '-' represents '÷' and '+' represents '-'. Find out the answer to the following question.
Among four cars, weight of C1 is twice the weight of C2. Weight of C3 is half of the weight of C2. C4 is 40 kg heavier than C2, but 40 kg lighter thanC1. What is the weight (in kg) of C4?