Sum of these unit vectors...?

Question

In a unit-vector notation, what is the sum of a = (4.00 m) i^ + (3.0 M)j^ and b = (-13.0 m)i^ + (7.0 m)j^ ? (the ^ next the the letters are hats, so i^ would be i hat)
What are the (b) magnitude and (c) direction of a + c (relative to i^)?

Answer 1

a+b= (-9m)i +(10m)j if this is c?
a+c= (-5m)i+13m j
Magnitude= m*sqrt(25+169) =m*sqrt(194)
tan@=-13/5 so @=-1.2036 rad