Wow!!thats a word from the old english that made it
Let 'a' be the point and 'A' be the reflection of point 'a' through line x= -3
we know, (a+A)/2 (mid point of line aA) should lie on line x= -3
so by using this, we calculate vertices of reflected shape of MAST, we get
(-3,-1), (-3,2),(-5,3) and (-7,1)