Currect size relay for E-STOP

I intend to clamp a wire-wound resistor across the filter cap on my
68.7v DC PS.

I have 3 75v 2A servos running. Assume the purpose of this is to
absorb energy when the e-stop is pressed and the AC is cut to the PS.

If I use a relay rated at 25A @ 28v DC does this mean that it is
good for 10A @ 70v DC by using OHM's law?

P=E*I
28v * 25A = 700W

so

I=P/E

700W / 70v = 10A

Currect?

And is this enough, or do I need more?