Original total of n numbers = 40n.
After removing 28:
• New total = 40n − 28, count = n − 1.
• Average = (40n − 28) ÷ (n − 1) = 41.
• 40n − 28 = 41n − 41.
• 13 = n.
After adding y (back to original count n):
• Total = 40n − 28 + y, count = n.
• Average = (40n − 28 + y) ÷ n = 42.
• 40(13) − 28 + y = 42(13).
• 520 − 28 + y = 546.
• 492 + y = 546, so y = 54.
Final Answer: n = 13, y = 54