$$F\left(x;\mathrm{A.},B\right)=\{\begin{array}{ll}1.,\hfill & x\le \mathrm{A.}\hfill \\ 1.-2.{\left(\frac{x-\mathrm{A.}}{B-\mathrm{A.}}\right)}^{2.},\hfill & \mathrm{A.}\le x\le \frac{\mathrm{A.}+B}{2.}\hfill \\ \text{2.}{\left(\frac{x-B}{B-\mathrm{A.}}\right)}^{\text{2.}},\hfill & \frac{\mathrm{A.}+B}{2.}\le x\le B\hfill \\ 0\hfill & x\ge B\hfill \end{array}$$