Consider the continuous beam shown in Figure T$4\mathrm{.}2$ for which all elements are of the uniform section, thus El$=$constant. Implement the flexibility method by removing one vertical support $($at A or D$)$ to create a statically determinate system.

Figure T$4\mathrm{.}2$

Answer: $R_A=-\frac{P}{4}[kN]$;$R_B=7\frac{P}{8}[kN]$;$R_D=3\frac{P}{8}[kN]$