A rigid horizontal bar ABC is supported by two columns BD and CE. BD is fixed at D, CE is pinned at E. A load $P$ is applied at distance $a$ from $B$. The columns are steel with $E = 200$ GPa and cross-section $1.5 \text{ cm} \times 1.5 \text{ cm}$. The lengths are: BD = 75 cm, CE = 125 cm. The value of $a$ for which both columns buckle simultaneously is \(\underline{\hspace{2cm}}\) cm (round off to one decimal place).
