Calculate the maximum current a 140 ohms, 1/2 watt

[Bobzombie]

I have looked thought all my notes and books and can not find the formal on how to do this question. I'm slowly going out of my mind any help would be great

Calculate the maximum current a 140 ohms, 1/2 watt resistor can have flowing through it safely.
Enter answer: mA

Then the 2nd part of the question is

What is the maximum e.m.f. which may be applied to the resistor above without causing overheating?

Enter Part 2 answer: V

[hotvette]

Don't you have some fundamental equations that relate voltage (V), resistance (R), current (I), and power (W)? You'll need them.