A 7kg iron shot is thrown 18m. What was its minimum initial kinetic energy?

Question

The answer is .62kJ. But how did they get it?

Answer 1

At minimum launch velocity v0 the launch angle theta = 45 deg.
v0 = sqrt(range*g/sin(2theta)) = 13.2816 m/s (see ref.)
KE = mv^2/2 = 617.4 J