6 Every day Eduardo tries to phone his friend. Every time he phones there is a \(50 \%\) chance that his friend will answer. If his friend answers, Eduardo does not phone again on that day. If his friend does not answer, Eduardo tries again in a few minutes' time. If his friend has not answered after 4 attempts, Eduardo does not try again on that day.

1. Draw a tree diagram to illustrate this situation.
2. Let \(X\) be the number of unanswered phone calls made by Eduardo on a day. Copy and complete the table showing the probability distribution of \(X\).

   \(x\)	0	1	2	3	4
   \(\mathrm { P } ( X = x )\)		\(\frac { 1 } { 4 }\)

3. Calculate the expected number of unanswered phone calls on a day.