two decimal places. $($Note that, as always, you should use the unrounded values for further calculations to avoid accumulating rounding error.$)$

Consider the encryption function defined by the following table, with plaintext distribution $P(A)=\frac{3}{4},P(B)=\frac{1}{4}$ and key distribution $P(k_1)=\frac{1}{4},P(k_2)=\frac{1}{4},P(k_3)=\frac{1}{2}.$