Solving a separable PDE with BC

[trap101]

So I have a question in terms of interpreting the boundary conditions for a PDE. It is question 4 in the attached picture.

My question is that usually when I have encountered BC problems I have been given that my boundary conditions equal a given value, in terms of the diffusion equation:

U(0,t) = U(l,t) = 0,

but as yuo can see they don't equate it to a constant. I know how to solve through for the PDE, but now I'm having trouble interpreting those BC in order to apply them to the ODEs I have obtained. Is there a constant I should assume that they equal?

 

[LCKurtz]

Show us what equations you get when you let $u(x,t) = X(x)T(t)$ and apply it to the two boundary conditions. And please type it here instead of giving an uneditable image.