Dot product and unit vectors

Hey,

I am working through work on the dot product and came across this question:

Let a be a unit vector and let |b| = 4. Let the angle between these two vectors be 30 degrees. Calculate (2a - b) DOT (5a + 3b).

*Don't know how to make the arrow above the letters, pretend it is above all a's and b's. Also, the DOT is how I am going to say dot product like the formula for the dot product of two vectors with an angle theta between them is: u DOT v = |u| |v| cos(theta).

I am unsure of how to proceed with this question. I am assuming that I put this through the DOT formula. But am unsure of how to set this up.

Help?