Bayes Theorem Probability with 3 events

Question

I am having trouble understanding how to set this one up, I don't need the full answer just how to set it up.

Sally is always running late to campus. The probability she is late to campus for when she uses her moped is $3\%$, for her car $10\%$ and then the train is $7\%$.
Question: Say the probability that Sally uses her moped is $0.7$, car $0.2$ , or train $0.1$. What is the probability Sally ends up being late? Please use extended Bayes Theorem.

My mistake, miss typed a number

Answer 1

Let $A_1$ be the event: Sally uses her moped

Let $A_2$ be the event: Sally uses her car

Let $A_3$ be the event: Sally uses the train

Let $B$ be the event: Sally is late

Using total probability formula:

$P(B) = \sum_{i=1}^n P(B|A_i)P(A_i) = P(B|A_1)P(A_1) + P(B|A_2)P(A_2) + P(B|A_3)P(A_3)$