An RAE cannot be directly converted into an IU without knowing the source(s) of vitamin A. For example, the RDA of 900 mcg RAE for adolescent and adult men is equivalent to 3,000 IU if the food or supplement source is preformed vitamin A (retinol).
On the other hand, an Associate degree is a title conferred on a student when he completes a college study. Diploma is usually given in vocational or professional courses, like designing, pharmacy and engineering. High schools, trade colleges and professional schools confer Diploma certificates.
Masters as well as PGD, both are beneficial after graduation in mechanical engineering. But the difference between a Postgraduate Certificate, a Postgraduate Diploma and a Masters (MA or MSc or MS) is in the amount of credits the course contains. A general masters degree contains a greater number of credits (usually 1.5 times) than a post graduate diploma.