Find the value of `lambda` so that the vectors `veca` and `vecb` are perpendicular to each other. `veca` = (6,2,-3), `vecb` = (1,-4,`lambda`)

Explanation

If `veca` and `vecb` are perpendicular `veca.vecb = 0`
`implies (6,2,-3).(1,-4,lambda) = 0`
`implies 6-8-3lambda = 0`
`implies -2-3lambda = 0 implies lambda = -2/3