Answer: 0.8242182 quarts of blood will be present in the brain at rest.
Solution:
According to question: 15% by volume of blood your brain gets at rest
if we are having 5.2 L of blood in our body , then blood present in our brain at rest:

if 1 L= 1.05669 quart
Then 0.78 L will be =0.78 L
1.05669 quart = 0.8242182 quarts
0.8242182 quarts of blood will be present in the brain at rest.