\( \begin{aligned}
C_\mathrm{Total} = &~\sum_{t=1}^{T} R_\mathrm{0} - \frac{A}{2} + A T \\
=&~R_\mathrm{0}T - \frac{A}{2}T + A \frac{T(T+1)}{2}
= R_\mathrm{0}T + \frac{1}{2}A T^2
\end{aligned} \)

I've seen worse.