A3. At the first school hour, the number of boys and girls in the class was in the ratio $3: 4$. When 4 more girls came to the class before the second school hour, and 4 boys left the class, the ratio became $2: 5$. How many more girls than boys were there in the class at the second school hour?
(A) 5
(B) 6
(C) 7
(D) 8
(E) 12