A file has =20,000 student records. A STUDENT record has the following fields: Name (30 bytes), Ssn (9 bytes), Address (40 bytes), PHONE (10 bytes), Birth_date (8 bytes), Sex (1 byte), Major_dept_code (4 bytes), Minor_dept_code (4 bytes), Class_code (4 bytes, integer), and Degree_program (3 bytes). Suppose that only 80 percent of the STUDENT records have a value for Phone, 85 percent for Major_dept_code, 15 percent for Minor_dept_code, and 90 percent for Degree_program; and suppose that we use a variable-length record file. Each record has a 1-byte field type for each field in the record, plus the 1-byte deletion marker and a 1-byte end-of-record marker. Suppose that we use a spanned record organization, where each block has a 5-byte pointer to the next block (this space is not used for record storage). Required:
a. Calculate the average record length R in bytes.
b. Calculate the number of blocks needed for the file, where the block size is 512 bytes.