Mr. Ramirez purchased 20 concert tickets for a total of $225. The concert tickets cost $15 for adults and $10 for children under the age of 12. Part A: Which system of equations represents the given scenario? Let a represent adults and c represent children.

A.10a + 15c = 20
a + c = 225

B.10a + 15c = 225
a + c = 20

C.15a + 10c = 225
a + c = 20

D.15a + 10c = 20
a + c = 225

Part B: What is the solution to the system of equations?
A.5 adults and 15 children
B.10 adults and 10 children
C.15 adults and 5 children
D.9 adults and 9 children