Audrey was granted stock appreciation rights in $10,000$ shares of company stock when the share price was $$50.$ If she exercised her rights when the share price was $$70,$ how much income, if any, must she recognize at that time?

$($Search Chapter $3)$

a$.$ $$0$

b$.$ $$200,000$

c$.$ $$500,000$

d$.$ $$700,000$