4 Each school-day morning, three students, Rita, Said and Ting, travel independently from their homes to the same school by one of three methods: walk, cycle or bus. The table shows the probabilities of their independent daily choices.
| \cline { 2 - 4 }
\multicolumn{1}{c|}{} | Walk | Cycle | Bus |
| Rita | 0.65 | 0.10 | 0.25 |
| Said | 0.40 | 0.45 | 0.15 |
| Ting | 0.25 | 0.55 | 0.20 |
- Calculate the probability that, on any given school-day morning:
- all 3 students walk to school;
- only Rita travels by bus to school;
- at least 2 of the 3 students cycle to school.
- Ursula, a friend of Rita, never travels to school by bus. The probability that:
Ursula walks to school when Rita walks to school is 0.9 ; Ursula cycles to school when Rita cycles to school is 0.7 .
Calculate the probability that, on any given school-day morning, Rita and Ursula travel to school by:
- the same method;
- different methods.