A flat sign is your answer
I think it's D but dont take my word for it
Answer:
27cm
Explanation:
24² + (72-r)² = (24+r)²
576 + 5184 -144r +r² = 576 +48r +r²
5184 = 192r
5184/192 = r = 27cm
Just put a paper over that picture and draw what u see through the paper