To answer to this question, we could use the following equation for dilutions:
As we know, the values provided by the problem are:
C1 = 3.89 M
V1 = 48 mL
V2 = 320 mL
C2 = ?
What we're going to do is to replace the values in the equation so we can solve for C2:
Therefore, the concentration of the new solution would be 0.58 M.