4 A \(\boldsymbol { \rho }\) trb station fid th tits \(\mathbf { d }\) ily sales，in litres，are \(\mathbf { n }\) mally \(\dot { \mathbf { d } }\) strib ed with mean ad stad rd d \(\dot { \mathbf { v } }\) atin \(\quad 0\)
（a）Fid 0 may dy 6 th \(\mathbf { y }\) ar（B d \(\mathbf { y }\) ）th d ily sales can b eq cted to e区 eed \(\boldsymbol { \theta }\) litres． Th d ily sales at an \(\mathbf { b } r \mathbf { p }\) trb station are \(X\) litres，we re \(X\) is \(\mathbf { n }\) mally \(\dot { \mathbf { d } }\) strib ed with mean \(m\) ad stad rd iv atird \(\quad t\) is g it h \(\mathrm { t } \mathrm { P } ( X > 0 = \mathbb { 0 }\)
（b）Fid by le \(6 m\) ．
(c) Fid th p b b lity th t d ily sales at th s p trb station ex eed \(\theta\) litres \(\mathbf { n }\) fewer th n 266 rach lyc \(b\) end \(y\).
[0pt] [ \(\beta\)