3.11 Auto insurance premiums:  Suppose a newspaper article states that the distribution of auto insurance premiums for residents of California is approximately normal with a mean of $1600. The article also states that 25% of California residents pay more than $1900.

a) What is the Z-score that corresponds to the top 25% (or the 75th percentile) of the standard normal distribution? (Keep 2 decimal places.)
b) What is the mean insurance cost?
c) What is the cuto↵ for the 75th percentile?
d) Identify the standard deviation of insurance premiums in California. (Keep 1 decimal place)