Please answer on excel and show workings

Write the null and alternative hypotheses to test each of the following situations: a) Recently, 15% of cars of a certain model have needed costly brake work after being driven between 50,000 and 100,000 miles. The car manufacturer hopes that the redesign of a brake component has solved this problem. b) A local newspaper article reports that, in 1990, 41% of CEOs had an MBA degree. Has the percentage increased? c) A market researcher for a cola company decides to field test a new flavour soft drink planning to market it only if he is sure that over 52% of the people like the flavour