Vector A = <1,-4> and vector B = <5,7>

a) Find the vector C=2A-B

For C I got <-3,1>

b) Find the magnitude of C

For this I got /square root 10/

c) Find 'Theta' the direction of C such that 0degrees is 'less than or equal to' "theta" < 360 degrees.

d) Find the angle between the vectors A and B...

The first two I just need verification but the last two I couldn't get

If anybody can help me...thanks.