Find the angle 0 between the vectors. u=(1, 1, 1, 0), v = (4, 4, 4, 4).

30 degrees

Step-by-step explanation:

u dot v=1*4+1*4+1*4+0*4=4+4+4+0=12

|u|=sqrt(1^2+1^2+1^2+0^2)=sqrt(3)

|v|=sqrt(4^2+4^2+4^2+4^2)=sqrt(4*4^2)=2*4=8

cos(theta)=u dot v/(|u||v|)

cos(theta)=12/(sqrt(3)*8)

cos(theta)=3/(sqrt(3)*2)

cos(theta)=sqrt(3)/2

theta=30 degrees

Initial balance = $4,000
In the first 5 months, b = 4000 + 1000t, for 0 ≤ t≤ 5
Thereafter
b = 4000 + 1000t (0≤t≤5)- 1000t (t>5) = -|1000t-5000|+9000

In addition,
After 3 moths;
b = 4000+1000*3 = 4000+3000 = $7000

After 7 moths;
b = 4000+1000*5-1000*2 = 4000+5000-2000 = $7000

Therefore, statements A, C and D are true for this situation.