Answer :
A counter clockwise rotation is given by:
[tex]\begin{gathered} x^{\prime}=x\cos (\theta)-y\sin (\theta) \\ y^{\prime}=x\sin (\theta)+y\cos (\theta) \end{gathered}[/tex]For a rotation of 90 degrees:
[tex]\begin{gathered} x^{\prime}=-y \\ y^{\prime}=x \end{gathered}[/tex]Therefore:
[tex]\begin{gathered} A(2,-1)->(-y,x)->A^{\prime}(1,2) \\ C(9,0)->(-y,x)->C^{\prime}(0,9) \\ T(-1,10)->(-y,x)->T^{\prime}(-10,-1) \end{gathered}[/tex]