6 A coin is biased so that the probability that it will show heads on any throw is \(\frac { 2 } { 3 }\). The coin is thrown repeatedly.
The number of throws up to and including the first head is denoted by \(X\). Find
- \(\mathrm { P } ( X = 4 )\),
- \(\mathrm { P } ( X < 4 )\),
- \(\mathrm { E } ( X )\).