Given,
O be the origin and the position vector of the point P be −i^−2j^+3k^,
So, OP=−i^−2j^+3k^
Also given the position vectors of the points A,B and C are −2i^+j^−3k^,2i^+4j^−2k^ and −4i^+2j^−k^
Now finding,
AB=4i^+3j^+k^
AC=−2i^+j^+2k^
And AB×AC=∣i^4−2j^31k^12∣
⇒AB×AC=5i^−10j^+10k^
Now finding the Projection of OP on vector perpendicular to \vec{AB}&\vec{AC} we get,
Projection=∣∣AB×AC∣OP⋅(AB×AC)∣
=51+4+45(−i^−2j^+3k^)(i^−2j^+2k^)=3