Here is the question i am having trouble with -

Calculate the entropy of an ideal gas as a function of U, V and n at constant mole number solely by using the conditions:

pV=nRT (1)

U=3/2*nRT (2)

dU=Tds-pdV at n=const. (3)

I Have gotten to the point where I have

dS=(1/T)dU+(p/T)dV+(u/T)dn

I know that I need to integrate but not sure what to do from here.

Any help would be greatly appreciated