Please show numerical calculations

1) There are 4 possible routes I take to work - R1, R2, R3 and R4. The probability that I will be late due to a traffic delay when I take R1 is 0.4, R2 is 0.3, and R3 is 0.2. I take each of these routes R1, R2, R3 and R4 with probabilities 40%, 30%, 20%, and 10% respectively. If I am late to work on average 30% of the time, a) What is the probability that I will be late when I take R4? b) If I am late to work on a given day, what is the probability that I took either R, or R2 on this day