iF thE ADmission priCE For A roCk ConCErt is rAisED From $25 to $30, CAusing tiCkEt sAlEs to Drop From 60000 to 40000, thE priCE ElAstiCity oF DEmAnD For tiCkEts is:
A．

A. -0.25.

B．

B. -0.50.

C．

C. -2.20.