Num of point of intersection

It is given that the equations if twostraight lines L1 and L2 are mx-3y+11=0
(where m is a constant )and 7x+5y-n=0(where n is a constant )respectively.
write down the values of mand n such that L1andL2 can satisfy the
following conditions
a.L1andL2 have infinitely many points of intersection
have infinitely many points of intersection
=>L1 is the same as L2
So
m/7=－3/5=11/－n
－5m=21，3n= 55
m=－21/5，n=55/3

b.L1andL2 have no points of intersection
have no points of intersection
=>
L1//L2
So
m/7=－3/5<>11/－n
－5m=21，3n<> 55
m=－21/5，n<>55/ 3

c.L1and L2 have one points of intersection
have one points of intersection
=>mx－3y=－11，7x+5y=n
m/7<>－3/ 5
m<>－21/5