Rate of charging

I’m currently stuck in the second question of part A. I feel like V_0=V_R+V_C and since V_R=(dQ)/(dt) R and V_C=(Q)/(C), so then dQ/dt must be (V_0 - (Q)/(C))/(R) but the answer wasn’t right. Could someone please help me? Thanks a lot!
https://isaacphysics.org/questions/maths_ch7_3_q7?stage=a_level