Solution:
Dimension of Mary's original photo = 3-inch by 4-inch
Area of this photo = 3 x 4 = 12 square inch
Cost for printing this photo = $0.80
5a.
The photo was enlarged by a linear factor of 5.
New Dimension of the enlargement = (3 x 5) inch by (4 x 5) inch = 15 by 20 inch
Area of the enlargement = 15 x 20 = 300 square inch
Thus, cost of enlarged photo =
Cost of enlarged photo = $20
5b.
Given that cost of Mary's mother enlarged photo = $12.86