please help

A parallel-plate capacitor with vacuum between its horizontal plates has a capacitance of 21.0 JF. A nonconducting liquid with dielectric constant 5.50 is poured into the space between the plates, filling up a fraction f of its volume. (a) Find the new capacitance as a function of f. (C. is in F. Use any variable or symbol stated above as necessary.) (b) What should you expect the capacitance to be when f = 0? UF Does your expression from part (a) agree with your answer? Yes O No (c) What capacitance should you expect when f = 1? UF Does the expression from part (a) agree with your answer? Yes O No