Circular speed at radius four gives negative specific energy. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Circular speed-square gives two joules per kilogram
The circular speed-square 4 gives specific kinetic energy 2.
2v2=24=2J/kg
Potential wins, so the specific energy is negative
Potential is negative 4 and total specific energy is negative 2.