For 2018, Roberta is a self-employed truck driver with earnings of $45,000 from her business. During the year, Roberta received $2,500 in interest income and dividends of $500. She also sold investment property and recognized a $1,500 gain. What is the amount of Roberta’s self-employment tax (Social Security and Medicare taxes) liability for 2018? 

a. $2,790 

b. $3,443 

c. $6,358 

d. $6,885 

e. $7,344