David bought 100 shares of a stock for $30 per share on 70% margin. Assume he holds the stock for one year, and his interest costs will be $100 over the holding period. Ignoring commissions, what is his total return on investment if the stock appreciates to $35 per share?
a) 23.33%
b) 33.33%
c) 43.33%
d) 53.33%