Assuming your property was placed in service in 2020, 40 years is just flat out not an option with either GDS or ADS. If using GDS, it's 27.5 years. If using ADS it's 30 years. Again, 40 years is no longer an option.
See IRS Publication 527 page 9 at https://www.irs.gov/pub/irs-pdf/p527.pdf
Take note that whatever method you use, then you must use the same method and depreciation period for all assets in the same class.
Finally, note that your selection must be in the first year the property is placed in service, and you can not change it later.
