On his way to work every morning, bob first takes the bus from his house, exits near his workplace, and walks the remaining distance. his time spent on the bus (x) is a random variable that follows a normal distribution, with mean µ = 20 minutes, and standard deviation  = 2 minutes, i. e., x ~ n(20, 2). likewise, his walking time (y) is also a random variable that follows a normal distribution, with mean µ = 10 minutes, and standard deviation  = 1.5 minutes, i. e., y ~ n(10, 1.5). find the probability that bob arrives at his workplace in 35 minutes or less. [hint: total time = x + y ~ recall the "general fact" on page 4.1-13, which is true for both discrete and continuous random variables.]