4) With regard to triangles BAE and CDE, they are similar by AAA. Both are right triangles (at angles A and D) and the angles at E are vertical angles (equal). AE is 3 times DE, so AB will be 3 times DC, hence 12 units.
The radius of circle B is 12.00 units.
5) Consider the attached diagram, which seems to match the problem statement. You will note that the radius MJ is arbitrary length, hence cannot be determined from the information given. (Consider what happens when you swap points M and K. The radius is different, but problem conditions are still met.)
