Two points (a, 3) and (5, b) are the opposite vertices of a rectangle. If the other two vertices lie on the line y =2x+c which passes through the point (a, b) then the value of c is

Mid point of the line joining the given points lie on the given line 3+b2=2a+52+c⇒2a+2c−b+7=0            (i)Also since the given line passes through (a, b)    b=2a+c                         (ii)Solving (i) and (ii) we get c=-7