What is the maximum profit that an investor can obtain from a strategy employing a long $830$ call and a short $850$ call over $6$ months? Interest rates are $0\mathrm{.}5\%$ per month.A$)$ $$6\mathrm{.}80$B$)$ $$7\mathrm{.}68$C$)$ $$9\mathrm{.}24$D$)$ $$12\mathrm{.}32$