Read the Nth Fixed Record

Write a function string nthRecord(const string& filename, int n) that opens filename with an fstream in ios::in | ios::binary mode, seeks the read position to byte n * 4, reads that one record with getline, and returns the three letters (without the newline).

Every record in the file is exactly 4 bytes: three uppercase letters followed by one newline. n is always a valid record index.

The test creates the file in binary mode, calls your function and prints the returned record on its own line. For a file with the lines AAA, BBB, CCC and nthRecord("records_a.txt", 1) it prints the output shown in Expected Output.

Do NOT write a main function.