If a,b and c are nonzero real numbers such that ab=2(a+b),bc=3(b+c) and ca=4(c+a) then the value of 5a+7b+c is :
18
72
108
120
If a, b, and c are nonzero real numbers such that ab = 2 (a + b), bc = 3( b + c) and ca = 4 (c + a) then the value of 5a + 7b + c is :