The least effect on the call price comes from doubling the risk-free rate from 3.0% to 6.0%, which increases the option value by less than $1.00 (about $0.785). The other changes produce larger increases: stock price +$5 raises the call by about $3.182, volatility from 20% to 30% raises it by about $2.778, and doubling time to expiration raises it by about $3.042. In general, option values are most sensitive to the underlying stock price, volatility, and time to expiration.