Ali is currently working as a human resource manager for a company and earns a good salary. He is planning to pursue a Master of Business Administration (MBA) degree. He recently received an offer from University A, which included the cost of tuition fees. If Ali decided to go for the MBA study, his company would stop paying his salary. At the same time, if Ali completed his MBA degree, he would earn a higher salary than his current one. Furthermore, Ali has recently purchased an apartment in the city and moved in. For Ali, when considering whether or not to go for the MBA study, the cost of tuition fees is referred to as: a. None of the given answers. b. Incremental cost. C. Incremental revenue. d. Opportunity cost. e. Sunk cost