BV is total Common Stk hlders equity/common stk outstanding
(6+20+5-10)/(4-.5)=6
Price is your MV or current price per share = 21
So P/B = 21/6 = 3.5
For common stk outstanding, you take only outstanding stks which is issued - anything that was repurchased as treasury. Be careful between issued and authorized. Authorized is max number of shares which management can issue.