If the system of equations `2x+3y=7,\ \ \ \ (a+b)x+(2a-b)y=21` has infinitely many solutions, then `a=1,\ \ b=5` (b) `a=5,\ \ b=1` (c) `a=-1,\ \ b=5` (d) `a=5,\ \ b=-1`

Options

A. a = 1, b = 5
B. a = 5, b =1
C. a = -1, b = 5
D. a = 5, b = -1

Answer

B