Muscat Company estimates bad debt expense at 0.20% of credit sales. The company reported accounts receivable and allowance for uncollectible accounts of $482,000 and $1560 respectively, at December 31, 2020. During 2021, Muscat Company's sales and collections were $320,000 and $315,000, respectively, and $1910 were bad debts written off. Muscat Company's 2021 bad debt expense is: a. $630. b. $640. c. $1660. d. $390