3 The random variable \(G\) has the distribution \(\mathbf { N } \left( \mu , \boldsymbol { \sigma } ^ { 2 } \right)\). One hundred observations of \(G\) are taken. The results are summarised in the following table.
| Interval | \(G < 40.0\) | \(40.0 \leqslant G < 60.0\) | \(G \geqslant 60.0\) |
| Frequency | 17 | 58 | 25 |
- By considering \(\mathrm { P } ( G < 40.0 )\), write down an equation involving \(\mu\) and \(\sigma\). [2]
- Find a second equation involving \(\mu\) and \(\sigma\). Hence calculate values for \(\mu\) and \(\sigma\). [4]
[0pt] - Explain why your answers are only estimates. [1]