Price per share of stocks A and B on January 1 for 6 years is shown below. What was the average yearly increase in the value of a share of stock A from 2005 to 2010 ?

Question

$\begin{array}{1 1} (a)\;\$2\\ (b)\;\$5\\ (c)\; \$10 \\(d)\; \$12 \end{array}$