Rhombus measurement help

The contents of 3838 cans of coke have a mean of x¯¯¯=12.15x¯=12.15. assume the contents of cans of coke have a normal distribution with standard deviation of σ=0.12.σ=0.12. find the value of the test statistic zz for the claim that the population mean is μ=12.μ=12.

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?

Me with this one question, and i'll upvote the brainliest answer