Anna's expenses for entertainment during a period of time can be described with a normally distributed random variable with mean SEK 720 and standard deviation SEK 30. Bella´s expenses for...

Extracted text: Anna's expenses for entertainment during a period of time can be described with a normally distributed random variable with mean SEK 720 and standard deviation SEK 30. Bella´s expenses for entertainment during the same time period can be described with a normally distributed random variable with mean SEK 640 and standard deviation SEK 25. Consider the total expenses for Anna over 12 time periods and the total expenses for Bella over 13 time periods. a) Find the probability that Bella´s total expenses are greater than Anna´s total expenses. b) Find the probability the difference between their total expenses is at most SEK 300.