The temperature outside at 6 a.m. was 45°. By 10 a.m. it had risen 12°. By 4 p.m. it had risen another 10%. At 9 p.m. the temperature had dropped 15º. What was the temperature at 9 p.m?

a. 42.25º
b. 43.85º
c. 40.50º
d. 41.65º