In an xy-coordinate plane, a line is defined by y = kx + 1. If (2, b), (a, 4), and (a, b+1) are three points on the line, where a and b are unknown, then k = ? Choose the correct choice from the following choices
A) 1/2  B) 1  C) 3/2  D) 2  E) 5/2
b=2k+1...(1)   b+1=ak+1...(2)   4=ak+1...(3)   Taking (2) and (3)   4=b+1   b=3   Taking (1)   3=2k+1   k=1   Answer : 1
<result>B</result>
In an xy-coordinate plane, a line is defined by y = kx + 1. If (2, b), (a, 4), and (a, b+1) are three points on the line, where a and b are unknown, then k = ?