A non-dividend paying stock currently trades for $22 and has an annualised return standard deviation of 25%. Given that the continuously compounded risk-free rate of return is 6% p.a,

I have just sold 600 European call options written over XYZ shares. The stock is currently trading for $21 a share and has standard deviation of 15% p.a. The options mature in 2 months and have a strike price of $22. The continuously compounded risk-free rate of return is 4% p.a. Explain exactly how I can trade today in the underlying shares to hedge my market risk. How often should I rebalance my portfolio?