Serena is a member of her employer's group disability insurance plan. Serena and her employer share the cost of the premium 50%/50% and the total premium paid on the plan to date has been $7,400. Serena made her first claim since joining that plan and received $21,000 in benefits this past year. How much of the disability income would be taxable to Serena?

a. $0

b. $3,700

c. $17,300

d. $21,000