iv$.$ For the given circuit, how much must be value of R$3$ to get maximum power?

v$.$ A circuit having $3$ resistors in series with values $R1=R,R2=2R$ and $R3=3R.$ Voltage drop across R$2$ is $20$ V $.$ What will be voltage across the battery?

vi$.$ A circuit having $3$ resistors in parallel with values $R1=R,R2=2R$ and $R3=3$R$.$ Voltage drop across R$2$ is $20$ V $.$ What will be total current in the circuit?

vii. A wire having current of $10$ A passing in $1$ hour, how much charge in the wire?

viii. A wire having current of $10$A passing in $1$ hour, how much Energy in the wire if the voltage across wire is $20$ V $?$