Answer
$B>A=C$
Work Step by Step
From the formula $Q = mh_f$, we know that the amount of heat necessary depends on both the mass and the heat of fusion. Plugging in the values from the problem, A has $h_f$ of $50 J/kg$, C has $h_f$ of $50 J/kg$, and B has $h_f$ of $60 J/kg$, so the order is $B>A=C$.
