The minimum number of capacitors (each of capacitance 2 `mu` F ) required to get an effective capacitance of 9 `mu` F is?

If two capacitors of capacitances 2 mu F and 6 mu F are put in series, the effective capacitance of the system is

If two capacitors of capacitances 2 mu F and 4 mu F are connected in parallel the effective capacitance of the system is :

Two capacitors each of 4 mu F capacitance are joined in parallel . The effective capacitance is

When a number of capcitors of equal capacitances are connected in series, the effective capacitance is 0.4 mu F and when they are connected in parallel, the effective capacitance is 90mu F . What is the capacitance of each capacitor ?