A group of students sat for a test. Their average mark was 74.5. Three students found out that their marks were wrongly recorded as 63 instead of 84. The mark increased to 76.3 after correcting the mistakes.
(a) How many students sat for the test?
(b) A student who was absent sat for the test when he came back to school. The average mark decreased to 75 when his marks was included. What was the total marks the class scored?