Answer and Explanation:
(A) In the event that U1 = C1 and U2 = C2,
at that point two get both same utility C1 must equal to C2
C1 + C2 = 90
substituting C1 in the place of C2 in the above equation we get
2C1 = 90
C1 = 90/2
C1 = 45
C2 = 45
Each one has utility = 45
(B) U1 = U2
C1(c1/c2) = c1*c2
c1 = c2^2
c1 + c2 = 90
substituting c1 = c2^2 in c1 + c2 = 90
c2^2 + c2 = 90
c2 = 9
c1 = 81
U1 = U2 = 981 = 729
(C) U1 = u2
(C1 - 5)({c1 - 5}/{c2 + 5}) = (c1 - 5)(c2 + 5)
C1 - 5 = (c2 + 5)^2
C1 - 5 = c2^2 + 25 + 10c2
C1 = c2^2 + 30 + 10c2
90 = c2^2 + 30 + 10c2 + c2
0 = c2^2 - 60 + 11c2
C2 = 4,-15
-15 not possible C2 = 4
C1 = 90 - 4 = 86
U1 = U2 = 729
(D) Due to satisfy their principle, gift decrease the consumption of individual 2 by same amount and Increase consumption of individual 1 by same amount.