Find $L_{\text {ave }}$ for the letters $X, Y$, and $Z$ and their probabilities $.05, .05$, and .9 and compare it to $L_{\text {Huf }}$ computed for single letters and pairs of letters, as in Figure 11.6. Does $L_{\mathrm{Huf}}$ satisfactorily approximate $L_{\text {ave }}$ ? How can we remedy the problem?