Minimise the note

Step 1: Velocity ratio (VR)
The velocity ratio for a wheel and axle is the ratio of the radius of the wheel to the radius of the axle.
$VR = \frac{R}{r}$
Given $R = 30\,\mathrm{cm}$, $r = 3\,\mathrm{cm}$,
$VR = \frac{30}{3} = 10$

Step 2: Mechanical advantage (MA)
The mechanical advantage is the ratio of load to effort.
$MA = \frac{W}{P}$
Given $W = 400\,\mathrm{N}$, $P = 50\,\mathrm{N}$,
$MA = \frac{400}{50} = 8$

Step 3: Efficiency ($\eta$)
The efficiency is given by
$\eta = \frac{MA}{VR} \times 100\%$
Substitute the values,
$\eta = \frac{8}{10} \times 100\% = 80\%$

Final answers:
$VR = 10, \quad MA = 8, \quad \eta = 80\%$