Solution:Let us assume ‘x’ as the marks obtained by sunita in the fifth examination.
Now, to receive grade 'A’ as the course sunita must obtain an average of 90 marks or move in the five examinations.
⇒ 368 + x ≥ 450
x ≥ 82
∴ sunita must obtain greater than as equal to 82 marks in the fifth examination.