The points A,B and C have position vectors given respectively

a= ( 7i+ 4j-2k)b= ( 5i+ 3j- 3k)c= ( 6i+ 5j- 4k)

a) Find the angle BAC

b) Find the area of the triangle ABC

i have dont part a) and got 60 degrees but i cant do part b)

thanks in advance!