Answer:
About 2.38 square feet of extra fabric: 1.25 of dark blue and 1.13 of light blue
Need $13.75 to complete template for white fabric
Explanation:
Template requires 18 square feet of white, 20 square feet of light blue and 21 square feet of dark blue.
She has more than enough for both shades of blue fabric.
She needs 5.85 square feet more of white fabric
Since it is $2.35 per square feet of white fabric, 2.35 * 5.85 = $13.75.
It will cost her $13.75 for more white fabric
Hope this helps!