I need to calculate R1, R2, R5 and I.

I calculated R1 = 8 ohms and R5 = 20 ohms with the help of P1(I1) and P5(U).

I then got the current at the resistor R5 which is 4 A

Now I only have to calculate the current and R2, but I just cant I tried with a lot of equasions and failed can someone

slove it or at least point me to the right direction ? Thanks in advanced