Isaac Physics C4a

I’ve been struggling to find the power in C4a.2. I’ve managed to find the total resistance and the pd by splitting the resistance in a way like a ratio, but still stuck on finding power. Any help would be appreciated. I also know the equation is power = voltage^2/resistance
https://isaacphysics.org/questions/phys19_c4a_q2?board=phys19_c4_add&stage=a_level

As you mentioned that you have found the p.d. for part B and I believe you know that p.d. across parallel circuits is the same, so you have p.d. and resistance, the power is ...