$$2$$ beds and $$4$$ chairs have a total mass of $$240$$$$\text{kg}$$. $$1$$ bed weighs as much as $$6$$ chairs. Find the mass of $$1$$ chair. 
选项为:A:$$12$$ $$\text{kg}$$  B:$$15$$ $$\text{kg}$$  C:$$24$$ $$\text{kg}$$  D:$$30$$ $$\text{kg}$$  请回答其中一个选项.