The common stock of the Holden Corporation has been trading in a narrow range around $55 per share for months, and you believe it is going to stay in that range for the next 4 months. The price of a 4-month put option with an exercise price of $55 is $4, and a call with the same expiration date and exercise price sells for $5. Selling a straddle would generate premium income of ____.

A. $900

B. $500

C. $1800

D. $400