One-third of her bonus was $900/3 = $<<900/3=300>>300.
After one year, stock A doubled in value and was worth $300*2 = $<<300*2=600>>600.
After one year, stock B doubled in value and was worth $300*2 = $<<300*2=600>>600.
After one year, stock C had lost half its value and was worth $300/2 = $<<300/2=150>>150.
Altogether, at the end of the year, Gwen's stocks were worth $600+$600+$150 = $<<600+600+150=1350>>1350
#### 1350