If T and R are tread and rise respectively of a stair, then_______________?
A. 2R + T = 60
B. R + 2 T = 60
C. 2R + T = 30
D. R + 2 T = 30
A. 2R + T = 60
B. R + 2 T = 60
C. 2R + T = 30
D. R + 2 T = 30