e) Density function \( \text{\textit{\textsf{f}}}(\text{\textit{\textsf{x}}})=\frac{1}{\beta^{\alpha}\overline{|(\alpha)}}\ \text{\textit{\textsf{x}}}^{\alpha-1}\text{\textit{\textsf{e}}}^{\text{\textit{\textsf{x}}}/\beta} \) where x > 0; α and β are positive parameters x: used and required time function measured in minutes α: form parameter β: scale parameter f(x): gamma function e: exponential function | h) Sensitivity index: \( S=\frac{1}{1-\alpha } \) tu = used time tr = required time |