For each population and sample, determine what value of sample means would indicate a significant event two

Question:

For each population and sample, determine what value of sample means would indicate a significant event two standard deviations from the population mean.
a. μ = 80, σ = 10, sample size n = 25
b. μ = 130, σ = 6, sample size n = 36
c. μ = 18, σ = 2, sample size n = 64
d. μ = 0.52, σ = 0.1, sample size n = 100