EM waves and blackbody radiation question

[AlaskanPow]

Homework Statement

A rectangular metal plate measures 0.20 m long and 0.3 m wide. The plate is heated to a temperature of 1,433 K by passing a current through it. Assuming that it behaves like a blackbody, how much power does the plate radiate under these conditions?

Homework Equations

P∝T^4 (power is proportional to the temperature raised to the fourth power)
Only relevant equation I can find in my textbook so far. I don't where to factor in the lengths in the question.

The Attempt at a Solution

Ive tried all sorts of combos of the equation i gave, but all of them are wrong. I have the same question with different numbers and the answer to that one but still don't know how to get it.ψ

 

[norhh]

Ok you might not heard about stefan boltzman law
P=σAT⁴.(where A is surface area)
Where σ is called stefan boltzman constant its value is 5.670373(21)×10⁻⁸ W m⁻² K⁻⁴.
Now find it it is easy.