Since diameter is always perpendicular to tangent at point of contact in circle,
in this case:
AC is perpendicular to BC
which makes triangle ABC right angled triangle,
So from Pythagoras theorem,
AC=√(AB²-BC²)
=√(12²-5²)
=√(144-25)
=√119
=10.9
Since radius is half the length of diameter:
AP= AC/2
=10.9/2
=5.45 (nearly equal to 5.5)
Answer: a) 5.5 units