Consider the case of Merton's jump-diffusion model where jumps always reduce the asset price to zero. Assume that the average number of jumps per year is λ.
Show that the price of a European call option is the same as in a world with no jumps except that the risk-free rate is r + λ rather than r. Does the possibility of jumps increase or reduce the value of the call option in this case?
(Hint: Value the option assuming no jumps and assuming one or more jumps. The probability of no jumps in time T is e-λT ).