27-Ann Torbert purchased a truck for $11,000 on January 1, 2014. The truck will have an estimated salvage value of $1,000 at the end of 5 years. Using the units-of-activity method, the balance in accumulated depreciation at December 31, 2015, can be computed by the following formula: (a) ($ 11,000 = Total estimated activity) * Units of activity for 2015. (b) ($ 10,000 - Total estimated activity) * Units of activity for 2015 (c) ($11,000 - Total estimated activity) * Units of activity for 2014 and 2015. (d) ($ 10,000 - Total estimated activity) * Units of activity for 2014 and 2015