A 0.5 kg wooden block is placed on top of a 1.0 kg wooden block. The coefficient of static friction between the two blocks is 0.35. The coefficient of kinetic friction between the lower block and the level table is 0.2. What is the maximum horizontal force that can be applied to the lower block without the upper block slipping?

I found the kinetic friction of the two blocks, which is 2.94N. I found the static friction of the upper block, which is 1.715 N. I don't know what to do next. Do you add them together? When I tried it, I got less than 8.1 N, which is the answer in the back.