Answer : There are total 13 questions out of which 10 is to be answered .The student can answer in the following ways:
⇒ 3 questions from part A and 4 from part B
⇒ 4 questions from part A and 3 from part B
⇒ 5 questions from part A and 2 from part B
⇒ 2 questions from part A and 5 from part B
⇒ total ways in the 1st case are 6C3 6C4
⇒ total ways in the 2nd case are 6C4 6C3
⇒ total ways in the 3rd case are 6C5 6C2
⇒ total ways in the 4th case are 6C2X 6C5
=6C4 X6C3+ 6C3 X6C4 X6C5 X6C2+ 6C2 X6C5
= 780 ways.