1. The problem statement, all variables and given/known data The problem is: Project the smaller ressonant cavity for which the frequency of 2.4 GHz is the fundamental mode. 2. Relevant equations The problem wants me to calculate the lenght a, b and c of this "microwave oven" 3. The attempt at a solution I'm sorry, but I have no idea of how to calculate these dimensions. I've been reading some books (Sadiku, Pozar, Ramo, etc) but they just give problems in which these dimensions are already given.