Hairbrain Products, Inc. had $595,000 and $550, 000, respectively, in its equipment account on January 1 and December 31. During the year, no assets were purchased. Which of the following is a likely explanation? Select one: a) Depreciation expense during the year is $45,000. b) Equipment with an original cost of $45,000 was sold during the year. c) Equipment was wrote down to market value during the year to $45,000. d) Equipment with a book value of $45,000 was sold during the year.