If a³+b³+c³-3abc=0, then find the value of \(\left(\frac{a^2}{bc} + \frac{b^2}{ac} - 3\right)\).
\(-\frac{c^2}{ab}\)
\(-\frac{c^2}{bc}\)
\(-\frac{c^3}{ba}\)
\(-\frac{c}{a}\)
P can do a piece of work in 60 days & Q can do the same work in 50 days. Find the ratio of working efficiencies of P to Q.
\( \frac{1}{3} \)
\( \frac{6}{5} \)
\( \frac{5}{6} \)
\( \frac{4}{5} \)