1. John is a GrabFood rider and his weekly income depends heavily on the weather condition. Assume each day can be classified as Rainy day (20%) or non-Rainy day (80%) and each day's weather is independent. John checks his past delivery history and estimates that he can earn 150SGD on a rainy day, but earn much less on a non-rainy day, about a half amount on a rainy day.

What is the average weekly income John can earn? (Ans: $630)

What is the standard deviation of the weekly income John can earn? (Ans: 79.37)

(Hint: The earning per day is a random variable by itself. The total income per week is the sum of seven independent such random variables.)

(Continue from Q3) John is thinking to be a full-time GrabFood rider to make a living. To maintain a good living quality in Singapore, each week's expenditure should be 700SGD at least. Assume each week is independent and there are 52 weeks in a year. What is the probability that John can earn more than 700SGD per week at least 8 weeks in a year? (Ans: 0.512)

(Hint: first find out what is the probability that John could earn more than $700 per week.)