How to compare two different enzymes with same Km?

I have a test today I study at HUJI and I encountered this question which I can't figure out: if two different enzymes have the same kM and the same substrate what can I say about the two?

  1. same Vmax
  2. dosn't have the same Vmax
  3. may or may not have the same Vmax
  4. the proportion between kM to Vmax has to be 0.5

Km is the concentration of the substrate at which the rate of the enzymatic reaction is equal to 0.5 * Vmax. Km alone says nothing about the actual value of Vmax…