Computers from a particular company are found to last on average for three years

Computers from a particular company are found to last on average for three years without any
hardware malfunction, with a standard deviation of two months. At least what percent of the
computers last between 30 months and 42 months?
Hints:
This is a Chebyshev problem because it doesn't say anything about normal distribution.
Step 1: Make sure everything is in the same unit. I suggest months.
Step 2: Find how many standard deviations from the mean 30 and 42 are.
Step 3: Substitute into Chebyshev's Theorem to find the percentage. (Hopefully you
remember and wrote down that k represents the number of standard deviations.)