I would approach this question by observing the present value of all cash flows (in and out) at every point in time. Lets first begin with the outflows then inflows.
$$PV_{\mathrm{Outflow}}=2C + \sum_{i=2}^{8}\frac{C}{(1+12\%)^i}.$$
$$PV_{\mathrm{Inflow}}=\sum_{i=1}^{4}\frac{800}{(1+12\%)^i}+\sum_{i=5}^{8}\frac{1200}{(1+12\%)^i}$$
Now: " **What value of C makes the inflow series equivalent to the outflow series** ". Thus the equation I am trying to solve is
$$PV_{\mathrm{Inflow}} = PV_{\mathrm{Outflow}},$$
implying that
$$ \sum_{i=1}^{4}\frac{800}{(1+12\%)^i}+\sum_{i=5}^{8}\frac{1200}{(1+12\%)^i} = 2C + \sum_{i=2}^{8}\frac{C}{(1+12\%)^i}.$$
Furthermore
$$C = \frac{\sum_{i=1}^{4}\frac{800}{(1+12\%)^i}+\sum_{i=5}^{8}\frac{1200}{(1+12\%)^i}}{2 + \sum_{i=2}^{8}\frac{1}{(1+12\%)^i}}.$$
$$C = \$781.30\ (\mathrm{2dp.})$$