G6.3 If a 31-day month is taken at random, find $c$, the probability that there are 5 Sundays in the month.
$\begin{array}{l}1^{\text {st }} \text { day }=\text { Sunday } \Rightarrow 29^{\text {th }} \text { day }=5^{\text {th }} \text { Sunday } \\ 1^{\text {st }} \text { day }=\text { Saturday } \Rightarrow 30^{\text {th }} \text { day }=5^{\text {th }} \text { Sunday } \\ 1^{\text {st }} \text { day }=\text { Friday } \Rightarrow 31^{\text {st }} \text { day }=5^{\text {th }} \text { Sunday } \\ \text { Probability }=\frac{3}{7}\end{array}$