A $70 \mathrm{~kg}$ man leaps vertically into the air from a crouching position. To take the leap the man pushes the ground with a constant force $F$ to raise himself. The center of gravity rises by $0.5 \mathrm{~m}$ before he leaps. After the leap the c.g. rises by another $1 \mathrm{~m}$. The maximum power delivered by the muscles is : (Take $\mathrm{g}=10 \mathrm{~ms}^{-2}$ )