What is the $pH$ of $10 \ L$ of a buffer solution containing $0.01 \ M \ NH_4Cl$ and $0.1 \ M \ NH_4OH$ having $pK_b$ of $5$?

Given below are two statements:
Statement $I$: $A$ buffer solution is the mixture of a salt and an acid or a base mixed in any particular quantities.
Statement $II$: Blood is a naturally occurring buffer solution whose $pH$ is maintained by $H_2CO_3 / HCO_3^{-}$ concentrations.
In the light of the above statements,choose the correct answer from the options given below.

For preparing a buffer solution of $pH = 5$ by mixing sodium acetate and acetic acid,the ratio of the concentration of salt and acid should be $(K_a = 10^{-5})$:-

$2 \ g$ acetic acid and $3 \ g$ sodium acetate are present in $100 \ mL$ aqueous solution. What will be the $pH$ of the solution if the ionisation constant of acetic acid is $1.8 \times 10^{-5}$?

The pH of a solution obtained by mixing $5 \text{ mL}$ of $0.1 \text{ M } NH_4OH$ solution with $250 \text{ mL}$ of $0.1 \text{ M } NH_4Cl$ solution is . . . . . . $\times 10^{-2}$.

Which buffer solution out of the following will have $pH > 7$?