Vector Equations Dot Product

Let a=2

∧

i

−3

∧

j

+4

∧

k

and b=7

∧

i

+

∧

j

−6

∧

k

. If r×a=r×b,r⋅(

∧

i

+2

∧

j

+

∧

k

)=−3, then. r⋅(2

∧

i

−3

∧

j

+

∧

k

) is equal to