What I did was convert all the capacitance into Xc's so that I could convert a Y network into a delta networks and treat them exactly like resistors and convert them back. Then I combined the capacitors except for the 3F and the C and subtracted the number from 5F and got 2.625F. Then I tried took the 3F and C series and tried the answers until I god 2.625F. The result was 21F. There are many ways of looking at this circuit.You can treat the circuit as an AC circuit and do nodal analysis, or thevenize, or do mesh currents, and more. The important thing is to remember exactly what a capacitor is and how it works. The rest is just numbers.