A share of stock is currently priced at $$20$ and will change with equal likelihood to either $$50$ or $$10.$ A call option with a $$25$ exercise price is available on the stock. How many shares of stock must be purchased to replicate the payoff from owning one call option?

A$)$ $$\mathrm{.}50$ shares

B$)$ $$\mathrm{.}75$ shares

C$)$ $$\mathrm{.}63$ shares

D$)$ $$1\mathrm{.}25$ shares