Two identical blocks A and B rest on different horizontal surfaces. Block A starts sliding when the applied horizontal force reaches 12N and then experiences a constant sliding friction of 9N. Block B starts sliding at 8N and its sliding friction is 6N. Which inference is correct?
a) Block A has both a higher coefficient of static friction and a higher coefficient of kinetic friction than block B.
b) Block A has a higher coefficient of static friction but a lower coefficient of kinetic friction than block B.
c) Blocks A and B have the same coefficients of static and kinetic friction.
d) Block A has a lower coefficient of static friction but a higher coefficient of kinetic friction than block B.