Find a vector of magnitude twice of `12hat(i)-5hat(j)` and antil-parallel ot `3hat(i)-4hat(j)`

Explanation

suppose `vec(a)=12hat(i)-5hat(j), vec(b)=3hat(i)-4hat(j)` required vector `vec(r)`.
`vec(r)=2|vec(a)|(-hatb)`
`=2xx(13)((-3hat(i)+4hat(j)))/(5)`
`=(26)/(5) (-3hat(i)+4hat(j))`