The teacher will be very surprised to see your correct solution 😉
_________
/ 50
x_1 = -I*4 / 14 + --
\/ z
_________
/ 50
x_2 = I*4 / 14 + --
\/ z
_________
/ 50
x_3 = -4 / 14 + --
\/ z
_________
/ 50
x_4 = 4 / 14 + --
\/ z
sum
_________ _________ _________ _________
/ 50 / 50 / 50 / 50
-I*4 / 14 + -- + I*4 / 14 + -- + -4 / 14 + -- + 4 / 14 + --
\/ z \/ z \/ z \/ z
=
0
product
_________ _________ _________ _________
/ 50 / 50 / 50 / 50
-I*4 / 14 + -- * I*4 / 14 + -- * -4 / 14 + -- * 4 / 14 + --
\/ z \/ z \/ z \/ z
=
50
-14 - --
z