Answer:
 
Step-by-step explanation:
Recall that a cosine function of the form  has the following:
 has the following: 
- amplitude A
- Frequeny  .
. 
- Phase shift 
- Midline D
So, in our case, we know that A=3,  (which implies that
(which implies that  ) and D=5. Since we are not said everything about the Phase shift, lets asumme that the Phase shift is 0. Hence C=0.
) and D=5. Since we are not said everything about the Phase shift, lets asumme that the Phase shift is 0. Hence C=0. 
Then, our desired function is 