$$240\div16=15\text{kg}$$ 
$$2$$ 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. 
a: $$12$$ $$\text{kg}$$ 
b: $$15$$ $$\text{kg}$$ 
c: $$24$$ $$\text{kg}$$ 
d: $$30$$ $$\text{kg}$$ 