A log of length 20 m, diameter 2 m, and specific weight 500n/m3 rests on a level ground. What is the work done (in Nm) to make it to stand vertical?
(a) $\pi \left ( 1^{2} \right )\left ( 200 \right )\left ( 50 \right )\left ( 20 \right )$
(b) $\pi \left ( 1^{2} \right )\left ( 200 \right )\left ( 50 \right )\left ( 10 \right )$
(c) $\pi \left ( 1^{2} \right )\left ( 200 \right )\left ( 50 \right )\left ( 9 \right )$
(d) $\pi \left ( 1^{2} \right )\left ( 200 \right )\left ( 50 \right )\left ( 8 \right )$