Consider:

(a) Stock trades for $100;

(b) Calls with exercise prices of $90, $100, and $110 trade at prices of $17.67, $10.45, and $6.82 respectively.

If a person buys a $90 call, writes two $100 calls, and buys a $110 call, what is the magnitude of her maximum loss? Please answer correctly up to two decimal places.