Applying Kirchoff's law to the first loop,we get
40i1 + (i1 - i2)60 + 20i3 = 0
5i1 - 3i2 + i3 = 0 ------(1)
For the second loop,we get
(i1 - i2) * 60 + 70i4 + 50i5 = 0
or 6i1 - 6i2 + 7i4 + 5i5 = 0 -------(2)
For the loop ABCDA,we get
40i1 + 70i4 + 20 = 0
or 4i1 + 7i4 = -2 -------(3)
For the loop ADCA,we get
20i3 + 50i5 + 20 = 0
or 2i3 + 5i5 = -2 ------(4)
Solving the above four equations,we get the values of i1,i2,i3,i4 and i5.The voltage at point B is
(60i2) and the potential at point D is (20i3 - 50i5).