Why is the answer 7 year, isn't the year to calculate the expense is 10 year?

Barkley Company has a piece of equipment that it has been depreciating for 3 years. The equipment originally was estimated to have a useful life of 8 years and at the beginning of the current year, Barkley determines that the equipment's life has been extended to 10 years. When Barkley calculates depreciation for the current year, how many years of life should be used to calculate the depreciation expense