\begin{figure}
    \centering
    \subcaptionbox{Basic Event}{%
        \begin{tikzpicture}
            \draw[white](-1.5,0) -- ++(3.0,0);
            \draw(0,1) circle(0.5) node(){BE};
            \draw(0.5,1.75) node(){$\lambda_\mathrm{BE}$};
            \draw[-Triangle](0,1.5) -- ++(0,0.5);
        \end{tikzpicture}%
    }\quad\quad\quad
    \subcaptionbox{Sum}{%
        \begin{tikzpicture}
            \draw[white](-1.5,0) -- ++(3.0,0);
            \draw(0,1) circle(0.5) node(){+};
            \draw(0.5,1.75) node(){$\lambda_\mathrm{Sum}$};
            \draw[-Triangle](0,1.5) -- ++(0,0.5);
            \draw[-Triangle](-0.95,0) -- ++(0,0.26) -- ++( 0.5,0.5);
            \draw[-Triangle](+0.95,0) -- ++(0,0.26) -- ++(-0.5,0.5);
            \draw(0,0.125) node(){...};
            \draw(-0.7,0.15) node(){$\lambda_0$};
            \draw( 0.7,0.15) node(){$\lambda_n$};
        \end{tikzpicture}%
    }
    
    \subcaptionbox{Coverage}{%
        \begin{tikzpicture}
            \draw (0,0) rectangle ++(3,2);
            \draw (1.5,0.5) node(){\textbf{Coverage}};
            \draw (0,1) -- ++(3,0);
            \draw (1.5,1.5) node(){$c$};
            \draw (1.375,-0.25) rectangle ++(0.25,0.25);
            \draw (1.5,-0.5) node(){$\lambda_\mathrm{in}$};
            \draw[fill=black] (0.75,2.0) rectangle ++(0.25,0.25);
            \draw (0.875,2.5) node(){$\lambda_\mathrm{RF}$};
            \draw[fill=black] (2.0,2.0) rectangle ++(0.25,0.25);
            \draw (2.125,2.5) node(){$\lambda_\mathrm{MPF,L}$};
        \end{tikzpicture}%
    }\quad\quad\quad
    \subcaptionbox{Split}{%
        \begin{tikzpicture}
            \draw (0,0) rectangle ++(3,2);
            \draw (1.5,0.5) node(){\textbf{Split}};
            \draw (0,1) -- ++(3,0);
            \draw (0.5,1.5) node(){$p_0$};
            \draw (1,1) -- ++(0,1);
            \draw (1.5,1.5) node(){...};
            \draw (2,1) -- ++(0,1);
            \draw (2.5,1.5) node(){$p_n$};
            \draw (1.375,-0.25) rectangle ++(0.25,0.25);
            \draw[fill=black] (0.375,2.0) rectangle ++(0.25,0.25);
            \draw[fill=black] (1.375,2.0) rectangle ++(0.25,0.25);
            \draw[fill=black] (2.375,2.0) rectangle ++(0.25,0.25);
            \draw (1.5,-0.5) node(){$\lambda_\mathrm{in}$};
            \draw (0.5,2.5) node(){$\lambda_{0}$};
            \draw (2.5,2.5) node(){$\lambda_{n}$};
        \end{tikzpicture}%
    }\quad\quad\quad
    \subcaptionbox{ASIL}{%
        \begin{tikzpicture}
            \draw (0,0) rectangle ++(2,2);
            \draw (1.0,1.5) node(){\textbf{ASIL}};
            \draw (0.5,-0.5) node(){\scriptsize $\lambda^\mathrm{RF}_\mathrm{SPF}$};
            \draw (1.5,-0.5) node(){\scriptsize $\lambda_\mathrm{MPF,L}$};
            \draw (0.375,-0.25) rectangle ++(0.25,0.25);
            \draw (1.375,-0.25) rectangle ++(0.25,0.25);
        \end{tikzpicture}%
    }
    
    \caption{Calculation Blocks for the Safety Methodology}
    \label{fig:blocks}
\end{figure}