Q$4($Chapter $11)(13$ marks$)$ Linden Technologies is considering the issuance of a $$1,000$ par value, $20-$year noncallable bond with a $7\mathrm{.}00\%$ annual coupon. The bond is priced at par value. The organization currently benefits from a marginal tax rate of $40\mathrm{.}00\%.$ However, there is speculation that Congress may revise the corporate tax rate to $25\mathrm{.}00\%.$ a$.$ Explain how the cost of debt calculation is affected by the change in tax rate and its significance in the WACC computation. $(3$ marks$)$

b$.$ Discuss the potential impact on Delta Publishing's capital structure and investment decisions if the new tax rate is implemented. $(3$ marks$)$

c$.$ Calculate the initial after$-$tax cost of debt under the current $40\mathrm{.}00\%$ tax rate. $(3$ marks$)$

d$.$ How much the cost of debt change if the new tax rate was adopted? $(4$ marks$)$