$13.$ Referring to the below items, which items outlined below are classified as ordinary concept income. $($a$)$ A special gift card awarded by an employer to its employee. $($b$)$ Sales commission received by an employee for hitting KPIs. $($c$)$ A temporary loan arranged by an employer. $($d$)$ Proceeds from selling the copyright to a book. The recipient was an employee accountant who wrote a novel in her spare time over a number of years. A$)($a$)$ only B$)($b$)$ only C$)($b$)$ and $($c$)$ D$)$ None