Balance after 6 months would be 900*(900+2%). You just need to evaluate it then you will get the answer. btw 2% comes from 4% because it's half of the year.
Here you go, hope I helped.
Angle 5 = 117° because it is vertical to angle 8
Angle 7 = 63° because it is symmetrical to angle 5
Angle 6 = 63° because it is vertical to angle 7.
Angle 1 = 117° because it is corresponding to angle 5.
Angle 2 = 63° because it is corresponding to angle 6.
Angle 3= 117° because it is corresponding to angle 8.
Angle 4 = 63° because it is corresponding to angle 7.