$[14]3.$ An ostrich $1\mathrm{.}5$ m tall is walking toward a street light $4$ m above the ground at a speed of $5\backslash (\backslash$mathrm$\{$m$\}/\backslash$mathrm$\{$s$\}\backslash ).$ How fast is the length of the ostrich's shadow decreasing? At what speed is the tip of the shadow moving? If $\backslash (\backslash$alpha $\backslash )$ is the angle between the light and the ground measured at the tip of the shadow, as shown in the picture, what is the rate of change of $\backslash (\backslash$alpha $\backslash )$ when the shadow is $1\mathrm{.}5$ m long?