Let $X$ be a non-empty set and let $s\ge1$ be a given real number. A function $d:$ X $\times$ X$\to$ ${R}^{+}$ , is called a b-metric provided that, for all x,y,z $\in$ X,
1) d(x,y)=0 iff x=y,
2)d(x,y)=d(y,x),
3)d(x,z)$\le$s[d(x,y)+d(y,z)].
A pair (X,d) is called b-metric space. İt is clear...