Which of the following wheel$-$and$-$axle machines is most efficient and what is the difference in the two efficiencies?

Machine A: has a wheel radius of $1\mathrm{.}4m$ and an axle diameter of $31cm,$ but requires an effort of $3\mathrm{.}5kN$ to move a $3$ tonne load.

Machine B: lifts a load that is exactly $13$ times the effort, while the wheel rope moves $14\mathrm{.}5$ times further than the load rope.

$($Ans$.$ Machine A; $3\mathrm{.}5\%)$