24 students collected money for donation. The average contribution was ₹50. Later on, their teacher also contributed some money. Now the average contribution is ₹56. The teacher’s contribution is:

₹200

Sum of money collected by students = 24 x 50 = 1200

Sum of money when teacher also contributed = 25 x 56 = 1400

Teacher's contribution = 1400 - 1200 = ₹200