Answer:
4/9
Step-by-step explanation:
The possibilities of transportation: (The first will be for morning, second will be for afternoon)
B, B
B, C
B, T
C, B
C, C
C, T
T, B
T, C
T, T
It is clearly seen that there are 9 transportation options.
(Using cab 1 time we have BC, CB, CT, TC. So four of the transportation methods use cab one time.)
Therefore, the probability that she will use a cab only once is 4/9.