Establish following isomorphisms (preferably, using Fundamental Homomorphism Theorem):
a. R[x] / <(x^2)+6> is congruent to C
b. Z[18] / < 6 bar> is congruent to Z[6]
c. Q[x] / <(x^2)+x+1> is congruent to Q[ sqrt 3 i]
e. F[x] / is congruent to F
f. Z[3]xZ[4] is congruent to Z[12]