Please answer the following questions: a$.$ Why do countries with worldwide tax systems give foreign tax credits? b$.$ In principle, countries can band together to create uniform tax laws to ensure that each dollar of income is taxed once and only once. What are the costs and benefits of such uniformity from the perspective of lawmakers? c$.$ Do low tax rates in a foreign country imply that expected after$-$tax rates of return on marginal investments should be higher than those on domestic investments? Explain.