What formula in cell C$5$ calculates the weighted average cost of capital $($WACC$)?$

a$.=C\frac{2}{1-C1}+C{3}^{*}C1*(1-C4)$

b$.=C{2}^{*}C1+C{3}^{*}(1-C4{)}^{**}(1-C1)$

C$.=C{2}^{**}(1-C1)+C{3}^{**}C1$

d$.=C{2}^{*}(1-C1)+C{3}^{*}(1-C4{)}^{*}C\frac{1}{1+C1}$